Composition for forming organic film, patterning process, and polymer

ABSTRACT

A composition for forming an organic film contains a polymer having a repeating unit shown by formula (1A) as a partial structure, and an organic solvent, where AR 1  and AR 2  represent a benzene ring or naphthalene ring optionally with a substituent; W 1  represents any in formula (1B), and the polymer optionally contains two or more kinds of W 1 ; W 2  represents a divalent organic group having 1 to 80 carbon atoms; R 1  represents a monovalent organic group having 1 to 10 carbon atoms and an unsaturated bond; and R 2  represents a monovalent organic group having 6 to 20 carbon atoms and one or more aromatic rings. This invention provides: an organic film composition which enables excellent film formability, high etching resistance, and excellent twisting resistance without impairing the resin-derived carbon content, and which contains less outgassing-causing sublimation component; a patterning process using the composition; and a polymer suitable for the composition.

TECHNICAL FIELD

The present invention relates to a composition for forming an organic film, a patterning process using the composition, and a polymer contained in the composition.

BACKGROUND ART

Recently, along with advancements toward higher integration and higher processing speed of semiconductor devices, a finer pattern rule has been required. In this situation, various techniques have been developed in regard to how patterning process can be performed more finely and precisely depending on light sources used in lithography with light exposure, which is a commonly-employed technique at present.

As the light source for lithography employed in resist pattern formation, light exposure using a g-line (436 nm) or an i-line (365 nm) of a mercury lamp is widely adopted for portions where the degree of integration is low. Meanwhile, for portions where the degree of integration is high and finer patterning is required, lithography using a KrF excimer laser (248 nm) or an ArF excimer laser (193 nm) with shorter wavelengths has also been practically used. Moreover, for the most-advanced generation requiring further finer patterning, lithography with extreme ultraviolet ray (EUV, 13.5 nm) is about to be put into practical use.

It is well known that in a monolayer resist method, which is employed as a typical resist patterning process, as the thinning of resist patterns progresses as described above, the ratio of a pattern height to a pattern line width (aspect ratio) is increased, and pattern collapse occurs due to the surface tension of a developer during development. It is known that, in this situation, a multilayer resist method, in which a pattern is formed by laminating films having different dry etching properties, is excellent in forming a pattern with a high aspect ratio on an uneven substrate. There have been developed: a two-layer resist method in which a photoresist layer made of a silicon-containing photosensitive polymer is combined with an underlayer made of an organic polymer containing carbon, hydrogen, and oxygen as main constituent elements, for example, a novolak polymer (Patent Document 1 etc.); and a three-layer resist method in which a photoresist layer made of an organic photosensitive polymer used in a monolayer resist method is combined with a middle layer made of a silicon-based polymer or a silicon-based CVD film, and an underlayer made of an organic polymer (Patent Document 2 etc.).

In this three-layer resist method, first, a fluorocarbon-based dry etching gas is used to transfer the pattern of the photoresist layer to the silicon-containing middle layer. Then, using the pattern as a mask, dry etching with an oxygen-containing gas is performed to transfer the pattern to the organic underlayer film containing carbon and hydrogen as main constituent elements. By dry etching using the resultant as a mask, the pattern is formed on a substrate to be processed. However, in semiconductor device manufacturing processes after the 20-nm generation, when the pattern is transferred to a substrate to be processed by dry etching using such an organic underlayer film pattern as a hard mask, phenomena are observed in which the underlayer film pattern is twisted and/or curved.

The carbon hard mask formed immediately above the substrate to be processed is generally an amorphous carbon (hereinafter CVD-C) film prepared by a CVD method using a methane gas, an ethane gas, an acetylene gas, or the like as raw materials. It is known that the amount of hydrogen atoms in the CVD-C film can be reduced quite small, and the CVD-C film is very effective against the twisting and curving of the pattern as described above. Nevertheless, it is also known that when the substrate to be processed used as a base has a step, it is difficult to fill such a step into a flat state due to the characteristics of the CVD process. As a result, when a substrate to be processed having a step is coated with a CVD-C film and then patterned with a photoresist, the step of the substrate to be processed causes the applied surface of the photoresist to have a step. This makes the photoresist film thickness non-uniform, and consequently the focus margin and the pattern profile during lithography degradated.

On the other hand, it is known that when the underlayer film serving as the carbon hard mask formed immediately above the substrate to be processed is formed by a spin coating method, there is an advantage that a step(s) of the uneven substrate can be filled into a flat state. Planarizing the substrate by using the underlayer film material reduces fluctuation in film thickness of a silicon-containing middle layer and a photoresist coated thereon, can increase the focus margin in lithography and can form a correct pattern.

Hence, there are demands for: a material of an organic underlayer film which allows formation of an organic underlayer film by a spin coating method, the organic underlayer film enabling formation of a film having high etching resistance in dry etching a substrate to be processed and high planarizing property on the substrate to be processed; and a method for forming such an organic underlayer film.

Conventionally, condensed resins using aromatic alcohols and carbonyl compounds such as ketones and aldehydes as condensing agents for a phenol compound or naphthol compound have been known as the underlayer film material for forming an organic film for multilayer resist methods. Examples of such condensed resins include a fluorene bisphenol novolak resin described in Patent Document 2, a bisphenol compound and a novolak resin thereof described in Patent Document 3, a novolak resin of an adamantane phenol compound described in Patent Document 4, a bisnaphthol compound and a novolak resin thereof described in Patent Document 5, and the like. The main skeletons of the resins used in these materials are naphthalene, fluorene, adamantane, or the like, each of which has high carbon density, but their etching resistance inevitably degradates due to the oxygen atom of the phenolic hydroxyl group.

Further, to prevent the etching resistance degradation, no heteroatom such as oxygen is incorporated into a resin for underlayer film material. As an example of such a resin, Patent Document 6 describes a resin having a fluorene structure. Nevertheless, to form a cured film, a methylol compound or the like is added as a crosslinking agent to a composition. For this reason, when this composition is used to form a cured film, even if the carbon content of the resin is increased, this increase is offset by the low carbon content of the crosslinking agent, resulting in the problem of etching resistance degradation.

Furthermore, as an underlayer film material containing neither such an additive as a crosslinking agent nor such heteroatom as oxygen to enhance etching resistance, Patent Document 7 describes an example of a resist underlayer film material using a single-molecular compound. Nonetheless, the use of such single-molecular compound has problems of coatability onto a substrate having complex shape, sublimation product originated from the low-molecular-weight compound during baking, and so forth. These bring new issues regarding the resulting cured organic film; some properties thereof such as heat resistance and etching resistance need to be improved.

CITATION LIST Patent Literature

-   Patent Document 1: JP H06-118651 A -   Patent Document 2: JP 2005-128509 A -   Patent Document 3: JP 2006-293298 A -   Patent Document 4: JP 2006-285095 A -   Patent Document 5: JP 2010-122656 A -   Patent Document 6: WO 2013/047106 A1 -   Patent Document 7: WO 2018/164267 A1

SUMMARY OF INVENTION Technical Problem

The present invention has been made to solve the above-described problems. An object of the present invention is to provide: a composition for forming an organic film, the composition containing a polymer with high carbon content and thermosetting properties as to enable high etching resistance and excellent twisting resistance without impairing the resin-derived carbon content and also enable the composition to have excellent film formability and less sublimation component, which otherwise results in outgassing; a patterning process using this composition; and a polymer suitable for such a composition for forming an organic film.

Solution to Problem

To achieve the object, the present invention provides a composition for forming an organic film, comprising:

a polymer containing a repeating unit shown by the following general formula (1A) as a partial structure; and

an organic solvent,

wherein AR₁ and AR₂ each represent a benzene ring or a naphthalene ring which optionally have a substituent; W₁ represents any in the following general formula (1B), and the polymer optionally contains two or more kinds of W₁ in combination; and W₂ represents a divalent organic group having 1 to 80 carbon atoms,

wherein each R₁ represents a monovalent organic group having 1 to 10 carbon atoms and an unsaturated bond; and R₂ represents a monovalent organic group having 6 to 20 carbon atoms and one or more aromatic rings.

When an organic film formed from this organic film composition containing the polymer having the partial structure of the repeating unit shown by the general formula (1A) is heated, a thermal crosslinking reaction takes place through the action of the substituent represented by W₁ on the fluorene ring, so that an organic film containing many condensed aromatic ring structures for exhibiting high etching resistance is successfully formed. Since the organic film thus formed contains many condensed aromatic ring structures with high carbon content, the organic film has high dry etching resistance besides filling characteristic by spin coating. Moreover, the repeating unit of the polymer has one or more crosslinking groups, so that these crosslinking groups are distributed over the polymer as a whole. This makes it possible to form a finer organic film than when a single-molecular compound is used. Accordingly, an organic film excellent in twisting resistance can be formed. Further, the polymer having a molecular-weight distribution is used instead of highly crystalline single-molecular compound, and thus excellent film formability is exhibited on substrates having complicated structures and made of various materials. Additionally, the content of the low-molecular-weight component as a source of sublimation product is so low that outgassing can be suppressed during baking.

In the general formula (1B), R₁ is preferably any in the following general formula (1C),

When R₁ in the general formula (1B) is a certain crosslinking group as above, the composition for forming an organic film forms an organic film having sufficient thermosetting properties as well as more excellent etching resistance, twisting resistance, solubility into a solvent, and filling and planarizing properties.

In the general formula (1B), R₂ is preferably any in the following general formula (1D),

When R₂ in the general formula (1B) is a certain crosslinking group as above, the composition for forming an organic film forms an organic film having sufficient thermosetting properties as well as more excellent etching resistance, twisting resistance, solubility into a solvent, and filling and planarizing properties.

In the general formula (1A), the divalent organic group represented by W₂ is preferably any in the following general formula (1E),

wherein AR₃ and AR₄ each represent a benzene ring or a naphthalene ring which optionally have a substituent; and W₃ represents a divalent organic group having 6 to 50 carbon atoms and one or more aromatic rings.

When the divalent organic group represented by W₂ in the general formula (1A) has a certain condensed carbon ring structure as above, the carbon density of the polymer can be increased, thereby enabling the composition for forming an organic film to further improve the etching resistance and twisting resistance.

In the general formula (1E), the divalent organic group represented by W₃ is preferably any in the following general formula,

When the divalent organic group represented by W₃ in the general formula (1E) is a certain functional group as above, the composition for forming an organic film forms an organic film having sufficient thermosetting properties as well as more excellent etching resistance, twisting resistance, solubility into a solvent, and filling and planarizing properties.

The polymer preferably has a weight-average molecular weight of 1000 to 5000.

The composition for forming an organic film containing such a polymer having a weight-average molecular weight in this range can suppress outgassing during baking without impairing the solubility into the organic solvent.

The organic solvent is preferably a mixture of one or more organic solvents each having a boiling point of lower than 180° C. and one or more organic solvents each having a boiling point of 180° C. or higher.

When the organic solvent is the mixture described as above, the addition of the high-boiling-point solvent(s) to the polymer imparts thermal flowability to the resulting organic film. Thus, the composition for forming an organic film has both high filling and planarizing properties.

The composition for forming an organic film preferably further comprises at least one of a surfactant and a plasticizer.

Incorporating the additive(s) makes the composition for forming an organic film more excellent in coatability and filling and planarizing properties.

The present invention provides a patterning process comprising the steps of:

forming an organic film by using the above-described composition for forming an organic film on a body to be processed;

forming a silicon-containing resist underlayer film by using a silicon-containing resist underlayer film material on the organic film;

forming a resist upper layer film by using a photoresist composition on the silicon-containing resist underlayer film;

forming a circuit pattern in the resist upper layer film;

transferring the pattern to the silicon-containing resist underlayer film by etching using the resist upper layer film having the formed circuit pattern as a mask;

transferring the pattern to the organic film by etching using the silicon-containing resist underlayer film having the transferred pattern as a mask; and forming the pattern in the body to be processed by etching using the organic film having the transferred pattern as a mask.

The patterning process according to the three-layer resist process described above makes it possible to precisely form a fine pattern in a substrate to be processed.

The present invention provides a patterning process comprising the steps of:

forming an organic film by using the above-described composition for forming an organic film on a body to be processed;

forming a silicon-containing resist underlayer film by using a silicon-containing resist underlayer film material on the organic film;

forming an organic antireflective coating (BARC) on the silicon-containing resist underlayer film;

forming a resist upper layer film by using a photoresist composition on the BARC;

forming a circuit pattern in the resist upper layer film;

successively transferring the pattern to the BARC and the silicon-containing resist underlayer film by etching using the resist upper layer film having the formed circuit pattern as a mask;

transferring the pattern to the organic film by etching using the silicon-containing resist underlayer film having the transferred pattern as a mask; and etching the body to be processed using the organic film having the transferred pattern as a mask to form the pattern in the body to be processed.

The patterning process according to the four-layer resist process described above makes it possible to further precisely form a fine pattern in a substrate to be processed.

The present invention provides a patterning process comprising the steps of:

forming an organic film by using the above-described composition for forming an organic film on a body to be processed;

forming an inorganic hard mask selected from a silicon oxide film, a silicon nitride film, and a silicon oxynitride film on the organic film;

forming a resist upper layer film by using a photoresist composition on the inorganic hard mask;

forming a circuit pattern in the resist upper layer film;

transferring the pattern to the inorganic hard mask by etching using the resist upper layer film having the formed circuit pattern as a mask;

transferring the pattern to the organic film by etching using the inorganic hard mask having the formed pattern as a mask; and etching the body to be processed using the organic film having the formed pattern as a mask to form the pattern in the body to be processed.

The patterning process according to this three-layer resist process makes it possible to precisely form a fine pattern in a substrate to be processed.

Further, the present invention provides a patterning process comprising the steps of:

forming an organic film by using the above-described composition for forming an organic film on a body to be processed;

forming an inorganic hard mask selected from a silicon oxide film, a silicon nitride film, and a silicon oxynitride film on the organic film;

forming a BARC on the inorganic hard mask;

forming a resist upper layer film by using a photoresist composition on the BARC;

forming a circuit pattern in the resist upper layer film;

successively transferring the pattern to the BARC and the inorganic hard mask by etching using the resist upper layer film having the formed circuit pattern as a mask;

transferring the pattern to the organic film by etching using the inorganic hard mask having the formed pattern as a mask; and etching the body to be processed using the organic film having the formed pattern as a mask to form the pattern in the body to be processed.

The patterning process according to this four-layer resist process makes it possible to more precisely form a fine pattern in a substrate to be processed.

The inorganic hard mask is preferably formed by a CVD method or an ALD method.

When the inorganic hard mask is formed by a CVD method or an ALD method, a fine pattern can be formed more precisely in a substrate to be processed.

The circuit pattern is preferably formed in the resist upper layer film by a photolithography with a wavelength of 10 nm or more and 300 nm or less, direct lithography with electron beam, nanoimprinting, or a combination thereof.

When these methods are employed as the method for forming the circuit pattern in the resist upper layer film, a fine pattern can be formed more precisely in a substrate to be processed.

Preferably, alkali development or organic solvent development is employed as a development method.

When the development method is performed using an alkali or organic solvent, it is possible to more precisely form a fine pattern in a substrate to be processed.

The body to be processed is preferably a semiconductor device substrate, a metal film, a metal carbide film, a metal oxide film, a metal nitride film, a metal oxycarbide film, or a metal oxynitride film.

In the present invention, the aforementioned bodies to be processed are usable, for example.

The metal is preferably silicon, titanium, tungsten, hafnium, zirconium, chromium, germanium, copper, silver, gold, aluminum, indium, gallium, arsenic, palladium, iron, tantalum, iridium, molybdenum, or an alloy thereof.

These can be used as the metal.

The present invention provides a polymer comprising a repeating unit shown by the following general formula (1A) as a partial structure,

wherein AR₁ and AR₂ each represent a benzene ring or a naphthalene ring which optionally have a substituent; W₁ represents any in the following general formula (1B), and the polymer optionally comprises two or more kinds of W₁ in combination; and W₂ represents a divalent organic group having 1 to 80 carbon atoms,

wherein each R₁ represents a monovalent organic group having 1 to 10 carbon atoms and an unsaturated bond; and R₂ represents a monovalent organic group having 6 to 20 carbon atoms and one or more aromatic rings.

This polymer has thermosetting property and the main chain is constituted of condensed aromatic ring structures with high carbon content. Thus, this component provides a composition for forming an organic film which can form an organic film having high curving resistance and high dry etching resistance.

In the general formula (1B), R₁ is preferably any in the following general formula (1C),

When R₁ in the general formula (1B) is a certain crosslinking group as above, the polymer contains at least one crosslinking group per repeating unit and is capable of forming a fine cured film, and therefore, the polymer is suitable for forming an organic film more excellent in etching resistance and twisting resistance.

In the general formula (1B), R₂ is preferably any in the following general formula (1D),

When R₂ in the general formula (1B) is a certain crosslinking group as above, the polymer contains at least one crosslinking group per repeating unit and is capable of forming a fine cured film, and therefore, the polymer is suitable for forming an organic film more excellent in etching resistance and twisting resistance.

In the general formula (1A), the divalent organic group represented by W₂ is preferably any in the following general formula (1E),

wherein AR₃ and AR₄ each represent a benzene ring or a naphthalene ring which optionally have a substituent; and W₃ represents a divalent organic group having 6 to 50 carbon atoms and one or more aromatic rings.

When the divalent organic group represented by W₂ in the general formula (1A) has a certain condensed carbon ring structure as above, the carbon density of the polymer can be increased, and steric hindrance by the cardo structure thereof prevents crystallization. Consequently, the film formability is improved, and heat resistance and etching resistance can be imparted without impairing thermal flowability.

In the general formula (1E), the divalent organic group represented by W₃ is preferably any in the following general formula,

When the divalent organic group represented by W₃ in the general formula (1E) is a certain functional group as above, the polymer serves a component that provides a composition for forming an organic film which has all of etching resistance, twisting resistance, and heat resistance.

Advantageous Effects of Invention

As described above, the inventive polymer has a thermal-crosslinking group in every repeating unit and the main skeleton thereof is constituted of condensed aromatic rings. Hence, the polymer is useful for forming an organic film excellent in etching resistance and twisting resistance. Moreover, the inventive composition for forming an organic film containing such polymer is a useful material for forming an organic film having excellent etching resistance and twisting resistance as well as various properties such as heat resistance, and filling and planarizing properties. Thus, the inventive composition is quite useful as a resist underlayer film material in multilayer resist processes, for example, a two-layer resist process, a three-layer resist process using a silicon-containing resist underlayer film, and a four-layer resist process using a silicon-containing resist underlayer film and an organic antireflective coating. Further, the inventive patterning processes make it possible to precisely form a fine pattern in a substrate to be processed in such multilayer resist processes.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows an exemplary process flow of the inventive patterning process.

FIG. 2 is a cross-sectional view for illustrating an exemplary organic film formed by applying the inventive organic film composition on a SiO₂ wafer substrate having a trench pattern.

DESCRIPTION OF EMBODIMENTS

As described above, there have been demands for the development of: a composition for forming an organic film, the composition containing a polymer with high carbon content and thermosetting property as to enable high etching resistance and excellent twisting resistance without impairing the resin-derived carbon content and also enable the composition to have excellent film formability and less sublimation component, which otherwise results in outgassing; a patterning process using this composition; and a polymer suitable for such a composition for forming an organic film.

The present inventors have earnestly studied the above-described object and consequently found the following facts. Specifically, a crosslinking reaction takes place by heating a polymer having a partial structure which is constituted of a condensed aromatic ring structure and a substituent having an unsaturated bond as a thermal-crosslinking group. An organic film composition containing this polymer and an organic solvent consequently forms an organic film which has excellent etching resistance and twisting resistance as well as various properties such as heat resistance, filling and planarizing properties, film formability, and low sublimation-component content. These findings have led to the completion of the present invention.

Specifically, the present invention provides a composition for forming an organic film, comprising:

a polymer containing a repeating unit shown by the following general formula (1A) as a partial structure; and

an organic solvent,

wherein AR₁ and AR₂ each represent a benzene ring or a naphthalene ring which optionally have a substituent; W₁ represents any in the following general formula (1B), and the polymer optionally contains two or more kinds of W₁ in combination; and W₂ represents a divalent organic group having 1 to 80 carbon atoms,

wherein each R₁ represents a monovalent organic group having 1 to 10 carbon atoms and an unsaturated bond; and R₂ represents a monovalent organic group having 6 to 20 carbon atoms and one or more aromatic rings.

Further, the present invention provides a polymer comprising a repeating unit shown by the following general formula (1A) as a partial structure,

wherein AR₁ and AR₂ each represent a benzene ring or a naphthalene ring which optionally have a substituent; W₁ represents any in the following general formula (1B), and the polymer optionally comprises two or more kinds of W₁ in combination; and W₂ represents a divalent organic group having 1 to 80 carbon atoms,

wherein each R₁ represents a monovalent organic group having 1 to 10 carbon atoms and an unsaturated bond; and R₂ represents a monovalent organic group having 6 to 20 carbon atoms and one or more aromatic rings.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto.

[Polymer]

The inventive composition for forming an organic film contains a polymer having a repeating unit shown by the following general formula (1A) as a partial structure.

In the general formula (1A), each of AR₁ and AR₂ is a benzene ring or a naphthalene ring which optionally have a substituent. W₁ is any in the following general formula (1B), and two or more kinds of W₁ may be used in combination. W₂ is a divalent organic group having 1 to 80 carbon atoms.

In the general formula (1B), R₁ is a monovalent organic group having 1 to 10 carbon atoms and an unsaturated bond, and R₂ is a monovalent organic group having 6 to 20 carbon atoms and one or more aromatic rings.

Examples of a partial structure constituted of W₁, AR₁, and AR₂ in the general formula (1A) of the polymer include the following. These optionally have a substituent on the aromatic rings thereof. Examples of the substituent include a vinyl group, an ethynyl group, an ethynylphenyl group, an allyl group, a propargyl group, an aryl group, an allyloxy group, a propargyloxy group, etc. Among the following structures, fluorene and benzofluorene structures are preferable in view of availability of the raw materials.

Examples of a partial structure having R₁ as a substituent among the partial structures represented by W₁ in the above general formula include the following. These optionally have a substituent on the aromatic rings thereof. Examples of the substituent include a hydroxyl group, a methyl group, a methoxy group, a nitro group, a halogen group, a trifluoromethyl group, etc.

Examples of a partial structure having R₂ as a substituent among the partial structures represented by W₁ in the above general formula include the following. These optionally have a substituent on the aromatic rings thereof. Examples of the substituent include a hydroxyl group, an alkyl group, a methoxy group, a nitro group, a halogen group, a trifluoromethyl group, an acetyl group, a phenyl group, etc.

Examples of a partial structure shown by W₂ in the above general formula include the following. These optionally have a substituent on the aromatic rings thereof. Examples of the substituent include a hydroxyl group, an alkyl group, a methoxy group, a nitro group, a halogen group, a trifluoromethyl group, an acetyl group, a vinyl group, an ethynyl group, an ethynylphenyl group, an allyl group, an aryl group, etc. In the following formulae, n1 to n4 each represent an integer of 2 to 10.

In the general formula (1B), R₁ is preferably any in the following general formula (1C) in view of curability and availability of the raw materials.

In the general formula (1B), R₂ is preferably any in the following general formula (1D) in view of curability and availability of the raw materials.

In the general formula (1A), the divalent organic group represented by W₂ is preferably any in the following general formula (1E) from the viewpoints of imparting heat resistance, thermal flowability, solubility into a solvent, and etching resistance.

In the general formula (1E), AR₃ and AR₄ each represent a benzene ring or a naphthalene ring which optionally have a substituent; and W₃ represents a divalent organic group having 6 to 50 carbon atoms and one or more aromatic rings.

Further, in the general formula (1E), the divalent organic group represented by W₃ is preferably any in the following general formula. The polymer having such a partial structure introduced therein provides a composition for forming an organic film which has all of etching resistance, twisting resistance, heat resistance, and solubility into a solvent.

The polymer has a weight-average molecular weight (Mw) of preferably 1000 to 5000, more preferably 1000 to 4000.

With such a molecular weight, the solubility of the polymer into the organic solvent can be guaranteed, and the generation of sublimation product can be suppressed during baking. Moreover, the polymer has favorable thermal flowability. Accordingly, the composition for forming an organic film can not only favorably fill a fine structure formed on a substrate but also form an organic film while planarizing the entire substrate.

[Polymer Production Method]

The inventive polymer containing a repeating unit shown by the general formula (1A) as a partial structure can be synthesized by polycondensation between a compound constituted of AR₁, AR₂, and W₁ as shown below and an aldehyde or ketone compound which correspond to W₂. In the following scheme, AR₁, AR₂, and W₁ are as defined above.

Moreover, the polymer having the partial structure of W₂ constituted of AR₃, AR₄, and W₃ can be synthesized by polycondensation using a tertiary alcohol or alkyl ether compound as shown below. In the following scheme, AR₁, AR₂, AR₃, AR₄, W₁, and W₃ are as defined above, and each R represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms.

The polymers can be obtained generally in an organic solvent in the presence of an acid catalyst at room temperature or under cooling or heating as necessary. Examples of the acid catalyst to be used include inorganic acids such as hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid, and heteropoly acid; organic acids such as oxalic acid, trifluoroacetic acid, methanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, and trifluoromethanesulfonic acid; and Lewis acids such as aluminum trichloride, aluminum ethoxide, aluminum isopropoxide, boron trifluoride, boron trichloride, boron tribromide, tin tetrachloride, tin tetrabromide, dibutyltin dichloride, dibutyltin dimethoxide, dibutyltin oxide, titanium tetrachloride, titanium tetrabromide, titanium(IV) methoxide, titanium(IV) ethoxide, titanium(IV) isopropoxide, and titanium(IV) oxide.

The solvent to be used is not particularly limited. Examples thereof include alcohols such as methanol, ethanol, isopropyl alcohol, butanol, ethylene glycol, propylene glycol, diethylene glycol, glycerol, ethylene glycol monomethyl ether, and propylene glycol monomethyl ether; ethers such as diethyl ether, dibutyl ether, diethylene glycol diethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, and 1,4-dioxane; chlorinated solvents such as methylene chloride, chloroform, dichloroethane, and trichloroethylene; hydrocarbons such as hexane, heptane, benzene, toluene, xylene, and cumene; nitriles such as acetonitrile; ketones such as acetone, ethyl methyl ketone, and isobutyl methyl ketone; esters such as ethyl acetate, n-butyl acetate, and propylene glycol methyl ether acetate; and non-protic polar solvents such as dimethylsulfoxide, N,N-dimethylformamide, and hexamethylphosphoric triamide. One kind of these can be used alone or mixture of two or more thereof can be used.

The reaction method includes a method in which the compound constituted of AR₁, AR₂, and W₁ and the aldehyde, tertiary alcohol, or the like are used as monomers, and such monomers and an acid catalyst are charged at once; a method in which the monomers are dispersed or dissolved, and then a catalyst is added at once or intermittently; a method in which a catalyst is diluted with a solvent and then added dropwise; a method in which a catalyst is dispersed or dissolved, and then the monomers are added at once or intermittently; and a method in which the monomers are diluted with a solvent and added dropwise. After completion of the reaction, the resultant may be diluted with an organic solvent and then subjected to liquid separation and washing to remove the catalyst having been used for the reaction and to collect the target product.

Further, in these reactions, another compound different from the above-described monomers but capable of polycondensation can be used to carry out co-polycondensation. Examples of such co-polycondensable compound include the following. These optionally have a substituent on the aromatic rings thereof. Examples of the substituent include a vinyl group, an ethynyl group, an ethynylphenyl group, an allyl group, a propargyl group, an aryl group, an allyloxy group, a propargyloxy group, etc. From the viewpoints of imparting etching resistance and solubility into a solvent, the polycondensable compound preferably has a naphthalene ring, a fluorene structure, or a carbazole structure. Such a compound can be added when the reaction takes place by the aforementioned method or at another timing, and subjected to the co-polycondensation.

The organic solvent used in the liquid separation and washing is not particularly limited, as long as it is capable of dissolving the target product and being separated into two layers when mixed with water. Examples of the organic solvent include hydrocarbons such as hexane, heptane, benzene, toluene, and xylene; esters such as ethyl acetate, n-butyl acetate, and propylene glycol methyl ether acetate; ketones such as methyl ethyl ketone, methyl amyl ketone, cyclohexanone, and methyl isobutyl ketone; ethers such as diethyl ether, diisopropyl ether, methyl-tert-butyl ether, and ethylcyclopentylmethyl ether; chlorinated solvents such as methylene chloride, chloroform, dichloroethane, and trichloroethylene; mixtures thereof; and the like. As the water used for washing in this event, generally, what is called deionized water or ultrapure water may be used. The washing may be performed once or more, preferably approximately once to five times, because washing ten times or more does not always produce the full washing effects thereof.

In the liquid separation and washing, the washing may be performed with a basic aqueous solution to remove acidic components in the system. Specific examples of the base include hydroxides of alkaline metals, carbonates of alkaline metals, hydroxides of alkali earth metals, carbonates of alkali earth metals, ammonia, organic ammonium, etc.

Further, in the liquid separation and washing, the washing may be performed with an acidic aqueous solution to remove metal impurities or basic components in the system. Specific examples of the acid include inorganic acids such as hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid, and heteropoly acid; organic acids such as oxalic acid, fumaric acid, maleic acid, trifluoroacetic acid, methanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, and trifluoromethanesulfonic acid; etc.

The liquid separation and washing may be performed with any one of the basic aqueous solution and the acidic aqueous solution, or can be performed with a combination of the two. The liquid separation and washing is preferably performed with the basic aqueous solution and the acidic aqueous solution in this order from the viewpoint of removing the metal impurities.

After the liquid separation and washing with the basic aqueous solution and/or acidic aqueous solution, washing with neutral water may be successively performed. This washing may be performed once or more, preferably approximately once to five times. As the neutral water, deionized water, ultrapure water, or the like as mentioned above may be used. The washing may be performed once or more, but if the washing is not performed sufficiently, the basic components and the acidic components may not be removed in some cases. The washing is performed preferably approximately once to five times because washing ten times or more does not always produce the full washing effects.

Further, the reaction product after the liquid separation operation can also be collected as a powder by concentrating and drying the solvent or crystallizing the reaction product under reduced pressure or normal pressure. Alternatively, the reaction product can be retained in a solution state with an appropriate concentration to improve the workability in preparing an organic film composition. The concentration at this point is preferably 0.1 to 50 mass %, more preferably 0.5 to 30 mass %. With such a concentration, the viscosity is hardly increased, making it possible to prevent degradation of the workability; in addition, since the amount of the solvent is not excessive, the solution can be prepared economically.

The solvent in this event is not particularly limited, as long as it is capable of dissolving the polymer. Specific examples of the solvent include ketones such as cyclohexanone and methyl-2-amyl ketone; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, and 1-ethoxy-2-propanol; ethers such as propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether, and diethylene glycol dimethyl ether; and esters such as propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate, and propylene glycol mono-tert-butyl ether acetate. One kind of these can be used alone or mixture of two or more kinds thereof can be used.

Further, as an alternative method for obtaining the polymer to be used in the inventive composition for forming an organic film, the polymer can also be obtained by a method as follows: first, a fluorene is polycondensed to obtain an intermediate (Step 1); then, the hydrogen atoms of the fluorene are substituted with a substituent(s) having R₁ or R₂ (Step 2). Note that, in the following schemes, AR₁, AR₂, AR₃, AR₄, W₃, R₁, and R₂ are as defined above.

[Step 1]

[Step 2]

These reactions are not particularly limited, as long as the given substituent(s) can be introduced. Examples of the reactions include a substitution reaction using a halide, tosylate, or mesylate of R₁, and a base catalyst; a condensation reaction using an aldehyde of R₂ and a base catalyst; and other similar methods. In the following scheme, X represents a halogen, a tosyl group, or a mesyl group.

Examples of the base catalyst used in the substitution reaction or condensation reaction include inorganic base compounds such as sodium hydrogen carbonate, sodium carbonate, potassium carbonate, calcium carbonate, cesium carbonate, sodium hydroxide, potassium hydroxide, sodium hydride, and potassium phosphate; organic amine compounds such as triethylamine, pyridine, and N-methylmorpholine; etc. One kind of these may be used alone or combination of two or more kinds thereof can be used.

A method as described above is applicable to the polymer having the partial structure of W₂ constituted of AR₃, AR₄, and W₃. Specifically, the polymer can be obtained by: polycondensing a fluorene to obtain an intermediate (Step 1); and then substituting the hydrogen atoms of the fluorene with a substituent(s) having R₁ or R₂ (Step 2).

[Step 1]

[Step 2]

Any solvent may be used in this event without particular limitation, as long as the solvent is inactive in the reaction. Examples of the solvent include ether-based solvents such as diethyl ether, tetrahydrofuran, and dioxane; aromatic solvents such as benzene, toluene, and xylene; acetonitrile, dimethylsulfoxide, N,N-dimethylformamide, N-methylpyrrolidone, water, etc. One kind of these can be used alone or mixture thereof can be used.

The reaction and collection methods for this polymer are the same as the reaction and collection methods for the polymer obtained by polycondensation between a compound constituted of AR₁, AR₂, and W₁ and an aldehyde or ketone compound corresponding to W₂.

In the preparation for the polymer obtained according to these methods for use in a composition for forming an organic film, one kind of various halides, tosylates, and mesylates can be used alone, or combination of two or more kinds thereof can be used, depending on the required performances. For example, compounds having a side chain structure for improving planarizing property, a rigid aromatic ring structure for improving etching resistance and heat resistance, or the like can be combined at a certain ratio. Therefore, these enable the compositions for forming an organic film using these polymers to achieve all of filling and planarizing properties and etching resistance at high levels.

As described above, when the inventive polymer containing a repeating unit shown by the general formula (1A) as a partial structure is used in a composition for forming an organic film, the composition enables high etching resistance and excellent twisting resistance.

<Composition for Forming Organic Film>

The present invention further provides a composition for forming an organic film, containing: the polymer containing a repeating unit shown by the general formula (1A) as a partial structure; and an organic solvent. Note that, in the inventive composition for forming an organic film, one kind of the inventive polymer containing a repeating unit shown by the general formula (1A) as a partial structure can be used alone or a mixture of two or more kinds thereof can be used.

The inventive composition for forming an organic film may be further blended with a modifier such as a blend compound or another polymer. The modifier mixed with the inventive composition for forming an organic film serves to improve the film-formability with spin coating and the filling property for a stepped substrate. Examples of such a modifier include novolak resins of phenol, o-cresol, m-cresol, p-cresol, 2,3-dimethylphenol, 2,5-dimethylphenol, 3,4-dimethylphenol, 3,5-dimethylphenol, 2,4-dimethylphenol, 2,6-dimethylphenol, 2,3,5-trimethylphenol, 3,4,5-trimethylphenol, 2-tert-butylphenol, 3-tert-butylphenol, 4-tert-butylphenol, 2-phenylphenol, 3-phenylphenol, 4-phenylphenol, 3,5-diphenylphenol, 2-naphthylphenol, 3-naphthylphenol, 4-naphthylphenol, 4-tritylphenol, resorcinol, 2-methylresorcinol, 4-methylresorcinol, 5-methylresorcinol, catechol, 4-tert-butylcatechol, 2-methoxyphenol, 3-methoxyphenol, 2-propylphenol, 3-propylphenol, 4-propylphenol, 2-isopropylphenol, 3-isopropylphenol, 4-isopropylphenol, 2-methoxy-5-methylphenol, 2-tert-butyl-5-methylphenol, pyrogallol, thymol, isothymol, 4,4′-(9H-fluorene-9-ylidene)bisphenol, 2,2′dimethyl-4,4′-(9H-fluorene-9-ylidene)bisphenol, 2,2′diallyl-4,4′-(9H-fluorene-9-ylidene)bisphenol, 2,2′difluoro-4,4′-(9H-fluorene-9-ylidene)bisphenol, 2,2′diphenyl-4,4′-(9H-fluorene-9-ylidene)bisphenol, 2,2′dimethoxy-4,4′-(9H-fluorene-9-ylidene)bisphenol, 2,3,2′,3′-tetrahydro-(1,1′)-spirobiindene-6,6′-diol, 3,3,3′,3′-tetramethyl-2,3,2′,3′-tetrahydro-(1,1′)-spirobiindene-6,6′-diol, 3,3,3′,3′,4,4′-hexamethyl-2,3,2′,3′-tetrahydro-(1,1′)-spirobiindene-6,6′-diol, 2,3,2′,3′-tetrahydro-(1,1′)-spirobiindene-5,5′-diol, 5,5′-dimethyl-3,3,3′,3′-tetramethyl-2,3,2′,3′-tetrahydro-(1,1′)-spirobiindene-6,6′-diol, 1-naphthol, 2-naphthol, 2-methyl-1-naphthol, 4-methoxy-1-naphthol, and 7-methoxy-2-naphthol, dihydroxynaphthalenes such as 1,5-dihydroxynaphthalene, 1,7-dihydroxynaphthalene, and 2,6-dihydroxynaphthalene, methyl 3-hydroxynaphthalene-2-carboxylate, indene, hydroxyindene, benzofuran, hydroxyanthracene, acenaphthylene, biphenyl, bisphenol, trisphenol, dicyclopentadiene, tetrahydroindene, 4-vinylcyclohexene, norbornadiene, 5-vinylnorborna-2-ene, α-pinene, β-pinene, limonene, etc.; and polyhydroxystyrene, polystyrene, polyvinylnaphthalene, polyvinylanthracene, polyvinylcarbazole, polyindene, polyacenaphthylene, polynorbornene, polycyclodecene, polytetracyclododecene, polynortricyclene, poly(meth)acrylate, and copolymers thereof. It is also possible to blend a naphthol dicyclopentadiene copolymer disclosed in JP 2004-205685 A, a fluorene bisphenol novolak resin disclosed in JP 2005-128509 A, an acenaphthylene copolymer disclosed in JP 2005-250434 A, fullerene having a phenol group disclosed in JP 2006-227391 A, a bisphenol compound and a novolak resin thereof disclosed in JP 2006-293298 A, a novolak resin of an adamantane phenol compound disclosed in JP 2006-285095 A, a bisnaphthol compound and a novolak resin thereof disclosed in JP 2010-122656 A, a fullerene resin compound disclosed in JP 2008-158002 A, or the like. The modifier is blended in an amount of preferably 0 to 1,000 parts by mass, more preferably 0 to 500 parts by mass, based on 100 parts by mass of the inventive polymer containing a repeating unit shown by the general formula (1A) as a partial structure.

[Organic Solvent]

The organic solvent usable in the inventive composition for forming an organic film is not particularly limited, as long as the organic solvent is capable of dissolving the polymer containing a repeating unit shown by the general formula (1A) as a partial structure, an acid generator, a crosslinking agent, and other additives, for example. Specifically, a solvent having a boiling point of lower than 180° C. can be used, such as solvents disclosed in paragraphs (0091) to (0092) of JP 2007-199653 A. Above all, it is preferable to use propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, 2-heptanone, cyclopentanone, cyclohexanone, and a mixture of two or more thereof.

Such a composition can be applied by spin coating. Since the inventive polymer containing a repeating unit shown by the general formula (1A) as a partial structure is incorporated as described above, the composition for forming an organic film has favorable dry etching resistance as well as heat resistance and high filling and planarizing properties.

Further, in the inventive composition for forming an organic film, it is also possible to add, as a component of the organic solvent, a high-boiling-point solvent having a boiling point of 180° C. or higher to the above-described solvent having a boiling point of lower than 180° C. (a mixture of the solvent having a boiling point of lower than 180° C. and the solvent having a boiling point of 180° C. or higher). The high-boiling-point organic solvent is not particularly limited to hydrocarbons, alcohols, ketones, esters, ethers, chlorinated solvents, and so forth, as long as the high-boiling-point organic solvent is capable of dissolving the polymer containing a repeating unit shown by the general formula (1A) as a partial structure. Specific examples of the high-boiling-point organic solvent include 1-octanol, 2-ethylhexanol, 1-nonanol, 1-decanol, 1-undecanol, ethylene glycol, 1,2-propylene glycol, 1,3-butylene glycol, 2,4-pentanediol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, 2,4-heptanediol, 2-ethyl-1,3-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, glycerin, n-nonyl acetate, ethylene glycol monohexyl ether, ethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol monoisobutyl ether, diethylene glycol monohexyl ether, diethylene glycol monophenyl ether, diethylene glycol monobenzyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol butylmethyl ether, triethylene glycol dimethyl ether, triethylene glycol monomethyl ether, triethylene glycol-n-butyl ether, triethylene glycol butylmethyl ether, triethylene glycol diacetate, tetraethylene glycol dimethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-n-butyl ether, tripropylene glycol dimethyl ether, tripropylene glycol monomethyl ether, tripropylene glycol mono-n-propyl ether, tripropylene glycol mono-n-butyl ether, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, triacetin, propylene glycol diacetate, dipropylene glycol monomethyl ether acetate, dipropylene glycol methyl-n-propyl ether, dipropylene glycol methyl ether acetate, 1,4-butanediol diacetate, 1,3-butylene glycol diacetate, 1,6-hexanediol diacetate, triethylene glycol diacetate, γ-butyrolactone, dihexyl malonate, diethyl succinate, dipropyl succinate, dibutyl succinate, dihexyl succinate, dimethyl adipate, diethyl adipate, dibutyl adipate, etc. One kind of these may be used alone, or mixture thereof may be used.

The boiling point of the high-boiling-point solvent may be appropriately selected according to the temperature at which the composition for forming an organic film is heated. The boiling point of the high-boiling-point solvent to be added is preferably 180° C. to 300° C., more preferably 200° C. to 300° C. The boiling point of 180° C. or higher prevents the evaporation rate at baking (heating) from becoming excessive, which would otherwise occur if the boiling point is too low. Thus, sufficient thermal flowability can be obtained. Meanwhile, when the boiling point is 300° C. or less, the boiling point is not too high, so that the high-boiling-point solvent evaporates after baking and does not remain in the organic film. Thus, the organic film properties such as etching resistance are not affected.

When the high-boiling-point solvent is used, the high-boiling-point solvent is blended in an amount of preferably 1 to 30 parts by mass based on 100 parts by mass of the solvent having a boiling point of lower than 180° C. The high-boiling-point solvent in such a formulation amount prevents a failure in providing sufficient thermal flowability during baking, and degradation of the film properties such as etching resistance, which would otherwise occur if the high-boiling-point solvent remains in the organic film.

In such a composition for forming an organic film, the polymer containing a repeating unit shown by the general formula (1A) as a partial structure is provided with thermal flowability by adding the high-boiling-point solvent, so that the composition for forming an organic film has both high filling and planarizing properties.

[Other Additives]

In the inventive composition for forming an organic film, an acid generator can be added so as to further promote the curing reaction. The acid generator includes a material that generates an acid by thermal decomposition, and a material that generates an acid by light irradiation. Any acid generator can be added. Specifically, materials disclosed in paragraphs (0061) to (0085) of JP 2007-199653 A can be added, but the present invention is not limited thereto.

One kind of the acid generator, or a combination of two or more kinds thereof can be used. When the acid generator is added, the amount is preferably 0.05 to 50 parts by mass, more preferably 0.1 to 10 parts by mass, based on 100 parts by mass of the polymer having a partial structure shown by the general formula (1A).

To the inventive composition for forming an organic film, a surfactant can be added so as to improve the coating property in spin coating. As the surfactant, for example, those disclosed in (0142) to (0147) of JP 2009-269953 A can be used.

Moreover, to the inventive composition for forming an organic film, a crosslinking agent can also be added so as to increase the curability and to further suppress intermixing with an upper layer film. The crosslinking agent is not particularly limited, and known various types of crosslinking agents can be widely used. Examples thereof include melamine-based crosslinking agents, glycoluril-based crosslinking agents, benzoguanamine-based crosslinking agents, urea-based crosslinking agents, β-hydroxyalkylamide-based crosslinking agents, isocyanurate-based crosslinking agents, aziridine-based crosslinking agents, oxazoline-based crosslinking agents, and epoxy-based crosslinking agents.

Specific examples of the melamine-based crosslinking agents include hexamethoxymethylated melamine, hexabutoxymethylated melamine, alkoxy- and/or hydroxy-substituted derivatives thereof, and partial self-condensates thereof. Specific examples of the glycoluril-based crosslinking agents include tetramethoxymethylated glycoluril, tetrabutoxymethylated glycoluril, alkoxy- and/or hydroxy-substituted derivatives thereof, and partial self-condensates thereof. Specific examples of the benzoguanamine-based crosslinking agents include tetramethoxymethylated benzoguanamine, tetrabutoxymethylated benzoguanamine, alkoxy- and/or hydroxy-substituted derivatives thereof, and partial self-condensates thereof. Specific examples of the urea-based crosslinking agents include dimethoxymethylated dimethoxyethyleneurea, alkoxy- and/or hydroxy-substituted derivatives thereof, and partial self-condensates thereof. A specific example of the β-hydroxyalkylamide-based crosslinking agents includes N,N,N′,N′-tetra(2-hydroxyethyl)adipic acid amide. Specific examples of the isocyanurate-based crosslinking agents include triglycidyl isocyanurate and triallyl isocyanurate. Specific examples of the aziridine-based crosslinking agents include 4,4′-bis(ethyleneiminocarbonylamino)diphenylmethane and 2,2-bishydroxymethylbutanol-tris[3-(1-aziridinyl)propionate]. Specific examples of the oxazoline-based crosslinking agents include 2,2′-isopropylidenebis(4-benzyl-2-oxazoline), 2,2′-isopropylidenebis(4-phenyl-2-oxazoline), 2,2′-methylenebis4,5-diphenyl-2-oxazoline, 2,2′-methylenebis-4-phenyl-2-oxazoline, 2,2′-methylenebis-4-tert-butyl-2-oxazoline, 2,2′-bis(2-oxazoline), 1,3-phenylenebis(2-oxazoline), 1,4-phenylenebis(2-oxazoline), and a 2-isopropenyloxazoline copolymer. Specific examples of the epoxy-based crosslinking agents include diglycidyl ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,4-cyclohexanedimethanol diglycidyl ether, poly(glycidyl methacrylate), trimethylolethane triglycidyl ether, trimethylolpropane triglycidyl ether, and pentaerythritol tetraglycidyl ether.

Further, to the inventive composition for forming an organic film, a plasticizer can be added so as to further improve the planarizing and filling properties. The plasticizer is not particularly limited, and known various types of plasticizers can be widely used. Examples thereof include low-molecular-weight compounds such as phthalic acid esters, adipic acid esters, phosphoric acid esters, trimellitic acid esters, and citric acid esters; and polymers such as polyethers, polyesters, and polyacetal-based polymers disclosed in JP 2013-253227 A.

Further, like the plasticizer, as an additive for imparting the filling and planarizing properties to the inventive composition for forming an organic film, it is preferable to use, for example, liquid additives having polyethylene glycol or polypropylene glycol structure, or thermo-decomposable polymers having a weight loss ratio between 30° C. and 250° C. of 40 mass % or more and a weight-average molecular weight of 300 to 200,000. The thermo-decomposable polymers preferably contain a repeating unit having an acetal structure shown by the following general formula (DP1) or (DP1a).

In the formula, R₆ represents a hydrogen atom or a saturated or unsaturated monovalent organic group having 1 to 30 carbon atoms which may be substituted. Y₁ represents a saturated or unsaturated divalent organic group having 2 to 30 carbon atoms.

In the formula, R_(ha) represents an alkyl group having 1 to 4 carbon atoms. Y^(a) represents a saturated or unsaturated divalent hydrocarbon group having 4 to 10 carbon atoms which may have an ether bond. “n” represents an average repeating unit number of 3 to 500.

Note that one kind of the inventive composition for forming an organic film can be used, or two or more kinds thereof can be used in combination. The composition for forming an organic film can be used as a resist underlayer film material or a planarizing material for manufacturing a semiconductor device.

Moreover, the inventive composition for forming an organic film is quite useful as a resist underlayer film material for multilayer resist processes such as a two-layer resist process, a three-layer resist process using a silicon-containing middle layer film, and a four-layer resist process using a silicon-containing inorganic hard mask middle layer film and an organic antireflective coating.

<Method for Forming Organic Film>

In the present invention, the composition for forming an organic film can be used to form an organic film which serves as a resist underlayer film in a multilayer resist film used in lithography or a planarizing film for manufacturing a semiconductor.

In the present invention, a substrate to be processed is coated with the composition for forming an organic film by a spin coating method etc. By employing a method like spin coating method, favorable filling property can be obtained. After the spin coating, baking (heating) is performed to evaporate the solvent and to promote the crosslinking reaction, thereby preventing the mixing with a resist upper layer film or a resist middle layer film. The baking is preferably performed at 100° C. or more and 600° C. or less within 10 to 600 seconds, more preferably at 200° C. or more and 500° C. or less within 10 to 300 seconds. In considering the influences of device damage and wafer deformation, the upper limit of the heating temperature in lithographic wafer process is preferably 600° C. or less, more preferably 500° C. or less.

Moreover, in the present invention, after a substrate to be processed is coated with the inventive composition for forming an organic film by the spin coating method or the like as described above, an organic film can be formed by curing the composition for forming an organic film by baking in an atmosphere with an oxygen concentration of 0.1% or more and 21% or less.

A sufficiently cured organic film can be obtained by baking the inventive composition for forming an organic film in such an oxygen atmosphere. The atmosphere during the baking may be in air.

Nevertheless, it is preferable to introduce an inert gas such as N₂, Ar, or He to reduce oxygen amount from the viewpoint of preventing oxidation of the organic film. To prevent the oxidation, the oxygen concentration needs to be controlled, and is preferably 1000 ppm or less, more preferably 100 ppm or less. Preventing the oxidation of the organic film during baking is preferable because an increase in absorption and a decrease in etching resistance are prevented.

Because of the excellent filling and planarizing properties, the inventive composition for forming an organic film as described above can provide a flat organic film regardless of unevenness of a substrate to be processed. Accordingly, the inventive composition is quite useful in forming a flat organic film on a substrate to be processed which has a structure or a step with a height of 30 nm or more.

Note that the thickness of the organic film such as a resist underlayer film or a planarizing film for manufacturing a semiconductor device is appropriately determined and preferably 30 to 20,000 nm, more preferably 50 to 15,000 nm.

(Patterning Processes)

The present invention provides a patterning process according to a three-layer resist process using the composition for forming an organic film as described above. The patterning process is a method for forming a pattern in a substrate to be processed, and includes at least the following steps:

forming an organic film by using the inventive composition for forming an organic film on a substrate to be processed;

forming a silicon-containing resist underlayer film by using a resist underlayer film material containing silicon on the organic film;

forming a resist upper layer film by using a photoresist composition on the silicon-containing resist underlayer film;

forming a circuit pattern in the resist upper layer film;

transferring the pattern to the silicon-containing resist underlayer film by etching using the resist upper layer film having the formed circuit pattern as a mask;

transferring the pattern to the organic film by etching using the silicon-containing resist underlayer film having the transferred pattern as a mask; and

forming the pattern in the body to be processed by etching using the organic film having the transferred pattern as a mask.

The silicon-containing resist underlayer film in this three-layer resist process exhibits etching resistance to an oxygen gas or a hydrogen gas. Thus, when the organic film is dry-etched using the silicon-containing resist underlayer film as a mask in the three-layer resist process, the dry etching is preferably performed using an etching gas mainly containing an oxygen gas or a hydrogen gas.

As the silicon-containing resist underlayer film in the three-layer resist process, a polysiloxane-based underlayer film is also preferably used. The silicon-containing resist underlayer film having antireflective effect can suppress the reflection. Particularly, for 193-nm light exposure, a material containing many aromatic groups and having high etching selectivity relative to the substrate is used as an organic film, so that the k-value and thus the substrate reflection are increased; in contrast, the reflection can be suppressed by imparting absorption to the silicon-containing resist underlayer film so as to have an appropriate k-value, and the substrate reflection can be reduced to 0.5% or less. As the silicon-containing resist underlayer film having antireflective effect, a polysiloxane is preferably used which has anthracene for 248-nm and 157-nm light exposure, or a phenyl group or a light-absorbing group having a silicon-silicon bond for 193-nm light exposure in a pendant structure, and which is crosslinked by an acid or heat.

An organic antireflective coating (BARC) may be formed on the silicon-containing resist underlayer film. In this case, a pattern can be formed in a body to be processed through steps of:

forming an organic film by using the inventive composition for forming an organic film on a body to be processed;

forming a silicon-containing resist underlayer film by using a silicon-containing resist underlayer film material on the organic film;

forming a BARC on the silicon-containing resist underlayer film;

forming a resist upper layer film by using a photoresist composition on the BARC;

forming a circuit pattern in the resist upper layer film;

successively transferring the pattern to the BARC and the silicon-containing resist underlayer film by etching using the resist upper layer film having the formed circuit pattern as a mask;

transferring the pattern to the organic film by etching using the silicon-containing resist underlayer film having the transferred pattern as a mask; and

etching the body to be processed using the organic film having the transferred pattern as a mask to form the pattern in the body to be processed.

Alternatively, an inorganic hard mask may be formed as the resist underlayer film. In this case, a pattern can be formed in a body to be processed through steps of:

forming an organic film by using the inventive composition for forming an organic film on a body to be processed;

forming an inorganic hard mask selected from a silicon oxide film, a silicon nitride film, and a silicon oxynitride film on the organic film;

forming a resist upper layer film by using a photoresist composition on the inorganic hard mask;

forming a circuit pattern in the resist upper layer film;

transferring the pattern to the inorganic hard mask by etching using the resist upper layer film having the formed circuit pattern as a mask;

transferring the pattern to the organic film by etching using the inorganic hard mask having the formed pattern as a mask; and etching the body to be processed using the organic film having the formed pattern as a mask to form the pattern in the body to be processed.

In the case where an inorganic hard mask is formed on the organic film as described above, a silicon oxide film, a silicon nitride film, and a silicon oxynitride film (SiON film) can be formed by a CVD method, an ALD method, or the like. The method for forming the silicon nitride film is disclosed in, for example, JP 2002-334869 A and WO 2004/066377 A1. The film thickness of the inorganic hard mask is preferably 5 to 200 nm, more preferably 10 to 100 nm. As the inorganic hard mask, a SiON film is most preferably used which is effective as an antireflective film. When the SiON film is formed, the substrate temperature reaches 300 to 500° C. Hence, the underlayer film needs to withstand the temperature of 300 to 500° C. Since the compositions for forming an organic film used in the present invention have high heat resistance and can withstand high temperatures of 300° C. to 500° C., this enables the combination of the inorganic hard mask formed by a CVD method or an ALD method with the organic film formed by a spin coating method.

Moreover, the present invention is suitable for a four-layer resist process using BARC. In this case, a pattern can be formed in a body to be processed through steps of:

forming an organic film by using the inventive composition for forming an organic film on a body to be processed;

forming an inorganic hard mask selected from a silicon oxide film, a silicon nitride film, and a silicon oxynitride film on the organic film;

forming a BARC on the inorganic hard mask;

forming a resist upper layer film by using a photoresist composition on the BARC;

forming a circuit pattern in the resist upper layer film;

successively transferring the pattern to the BARC and the inorganic hard mask by etching using the resist upper layer film having the formed circuit pattern as a mask;

transferring the pattern to the organic film by etching using the inorganic hard mask having the formed pattern as a mask; and

etching the body to be processed using the organic film having the formed pattern as a mask to form the pattern in the body to be processed.

Although a photoresist film may be formed as a resist upper layer film on an inorganic hard mask, it is also possible to form a BARC on the inorganic hard mask by spin coating and then form the photoresist film on the BARC as described above. Particularly, when a SiON film is used as the inorganic hard mask, two antireflective films including the SiON film and the BARC make it possible to suppress the reflection even in liquid immersion exposure at a high NA exceeding 1.0. Another merit of the BARC formation is having an effect of reducing trailing of the photoresist pattern immediately above the SiON film.

The resist upper layer film in the three-layer resist process may be a positive type or a negative type, and any generally-used photoresist composition can be employed. After spin coating of the photoresist composition, pre-baking is preferably performed within ranges of 60 to 180° C. and 10 to 300 seconds. Then, light exposure, post-exposure bake (PEB), and development are performed according to conventional methods to obtain the resist pattern. Note that the thickness of the resist upper layer film is not particularly limited, but is preferably 30 to 500 nm, more preferably 50 to 400 nm.

In addition, the exposure light includes high energy beam with a wavelength of 300 nm or less; specifically, excimer laser of 248 nm, 193 nm, or 157 nm, soft X-ray of 3 to 20 nm, electron beam, X-ray, etc.

In the inventive patterning processes, a photolithography with a wavelength of 10 nm or more and 300 nm or less, direct lithography with electron beam, nanoimprinting, or a combination thereof is preferably employed as the method for forming the circuit pattern in the resist upper layer film.

Moreover, in the inventive patterning processes, alkali development or organic solvent development is preferably employed as the development method.

Next, using the resulting resist pattern as a mask, etching is performed. In the three-layer resist process, the silicon-containing resist underlayer film and the inorganic hard mask are etched using a fluorocarbon-based gas and the upper layer resist pattern as the mask. Thereby, a silicon-containing resist underlayer film pattern and an inorganic hard mask pattern are formed

Next, using the obtained silicon-containing resist underlayer film pattern and inorganic hard mask pattern as masks, the organic film is processed by etching.

Subsequently, the body to be processed (e.g. substrate to be processed) can be etched according to a conventional method. For example, the substrate to be processed made of SiO₂, SiN, or silica-based low-dielectric insulating film is etched mainly with a fluorocarbon-based gas; and p-Si, Al, or W is etched mainly with a chlorine- or bromine-based gas. When the substrate is processed by etching with a fluorocarbon-based gas, the silicon-containing resist underlayer film pattern in the three-layer resist process is removed when the substrate is processed. When the substrate is etched with a chlorine- or bromine-based gas, the silicon-containing resist underlayer film pattern needs to be removed by additional dry etching with a fluorocarbon-based gas after the substrate processing.

The organic film obtained from the inventive composition for forming an organic film is characterized by excellent etching resistance when the substrate to be processed is etched as described above.

In the inventive patterning processes, as the body to be processed, it is preferable to use a semiconductor device substrate, a metal film, a metal carbide film, a metal oxide film, a metal nitride film, a metal oxycarbide film, or a metal oxynitride film.

Further, as the metal, it is preferable to use silicon, titanium, tungsten, hafnium, zirconium, chromium, germanium, copper, silver, gold, aluminum, indium, gallium, arsenic, palladium, iron, tantalum, iridium, molybdenum, or an alloy thereof.

Note that the substrate to be processed is not particularly limited, and examples thereof include substrates made of Si, α-Si, p-Si, SiO₂, SiN, SiON, W, TiN, Al, or the like; these substrates coated with a layer to be processed; etc. Examples of the layer to be processed include various Low-k films made of Si, SiO₂, SiON, SiN, p-Si, α-Si, W, W—Si, Al, Cu, Al—Si, or the like; and stopper films thereof. Generally, the layer can be formed to have a thickness of preferably 50 to 10,000 nm, more preferably 100 to 5,000 nm. Note that when the layer to be processed is formed, the substrate and the layer to be processed are formed from different materials.

Furthermore, it is preferable to use the substrate to be processed which has a structure or step with a height of 30 nm or more.

Hereinbelow, an example of the three-layer resist process will be specifically described with reference to FIG. 1 .

As shown in FIG. 1(A), in the three-layer resist process, an organic film 3 is formed by using the inventive composition for forming an organic film on a layer 2 to be processed which has been stacked on a substrate 1. Then, a silicon-containing resist underlayer film 4 is formed, and a resist upper layer film 5 is formed thereon.

Next, as shown in FIG. 1(B), a predetermined portion 6 of the resist upper layer film is exposed to light, followed by PEB and development to form a resist pattern 5 a (FIG. 1(C)). Using the resulting resist pattern 5 a as a mask, the silicon-containing resist underlayer film 4 is etched with a CF-based gas. Thereby, a silicon-containing resist underlayer film pattern 4 a is formed (FIG. 1(D)). After the resist pattern 5 a is removed, the organic film 3 is etched with oxygen plasma using the resulting silicon-containing resist underlayer film pattern 4 a as a mask. Thereby, an organic film pattern 3 a is formed (FIG. 1(E)). Further, after the silicon-containing resist underlayer film pattern 4 a is removed, the layer 2 to be processed is etched using the organic film pattern 3 a as a mask. Thus, a pattern 2 a is formed (FIG. 1(F)).

When an inorganic hard mask is used, the inorganic hard mask is formed in place of the silicon-containing resist underlayer film 4. When a BARC is formed, the BARC layer is disposed between the silicon-containing resist underlayer film 4 or the inorganic hard mask and the resist upper layer film 5. The etching of the BARC starts before the etching of the silicon-containing resist underlayer film 4, but these etchings may be performed continuously. Alternatively, after the BARC is etched alone, for example, the etching apparatus is changed, and then the etching of the silicon-containing resist underlayer film 4 may be started.

As described above, the inventive patterning processes make it possible to precisely form a fine pattern in a substrate to be processed in the multilayer resist processes.

Example

Hereinafter, the present invention will be further specifically described by referring to Synthesis Examples, Comparative Synthesis Examples, Examples, and Comparative Examples. However, the present invention is not limited thereto. Note that gel permeation chromatography (GPC) was performed using tetrahydrofuran (THF) as an eluent to determine weight-average molecular weight (Mw) and number-average molecular weight (Mn) in terms of polystyrene, and dispersity (Mw/Mn) was calculated therefrom.

Polymers (A1) to (A12) incorporated into compositions for forming an organic film were synthesized using the following Fluorenes: (B1) to (B5) and Ketones, Aldehydes, Tertiary Alcohols: (C1) to (C11).

Fluorenes:

Ketones, Aldehydes, Tertiary Alcohols:

When a polymer having multiple substituents was synthesized, the proportions were expressed using “m” and “1” as in the following formulae.

Synthesis Example 1

Under a nitrogen atmosphere, a homogeneous solution with an inner temperature of 70° C. was prepared from 50.0 g of Compound (B1), 43.8 g of Compound (C1), 3.2 g of 3-mercaptopropionic acid, and 400 g of 1,2-dichloroethane. Then, 28.9 g of methanesulfonic acid was slowly added thereto for the reaction with an inner temperature of 70° C. for 24 hours. After cooling to room temperature, 1000 g of toluene was added, and the organic layer was washed six times with 300 g of pure water. Subsequently, the organic layer was evaporated under reduced pressure to dryness. To the residue, 300 g of THF was added to form a homogeneous solution. Thereafter, the polymer was reprecipitated with 1000 g of methanol. The precipitated polymer was separated by filtration, washed twice with 600 g of methanol, and collected. The collected polymer was vacuum dried at 70° C. Thus, (A1) was obtained. The weight-average molecular weight (Mw) and dispersity (Mw/Mn) of Polymer (A1) were determined in terms of polystyrene by GPC measurement using THF as an eluent. The results were Mw=2200 and Mw/Mn=2.48.

Synthesis Example 2

Under a nitrogen atmosphere, a homogeneous solution with an inner temperature of 70° C. was prepared from 50.0 g of Compound (B3), 22.6 g of Compound (C2), 2.2 g of 3-mercaptopropionic acid, and 400 g of 1,2-dichloroethane. Then, 19.8 g of methanesulfonic acid was slowly added thereto for the reaction with an inner temperature of 70° C. for 24 hours. After cooling to room temperature, 1000 g of toluene was added, and the organic layer was washed six times with 300 g of pure water. Subsequently, the organic layer was evaporated under reduced pressure to dryness. To the residue, 300 g of THF was added to form a homogeneous solution. Thereafter, the polymer was reprecipitated with 1000 g of methanol. The precipitated polymer was separated by filtration, washed twice with 600 g of methanol, and collected. The collected polymer was vacuum dried at 70° C. Thus, (A2) was obtained. The weight-average molecular weight (Mw) and dispersity (Mw/Mn) thereof were determined by GPC. The results were Mw=3440 and Mw/Mn=3.23.

Synthesis Example 3

Under a nitrogen atmosphere, a homogeneous solution with an inner temperature of 70° C. was prepared from 50.0 g of Compound (B1), 38.0 g of Compound (C3), 3.2 g of 3-mercaptopropionic acid, and 400 g of 1,2-dichloroethane. Then, 28.9 g of methanesulfonic acid was slowly added thereto for the reaction with an inner temperature of 70° C. for 24 hours. After cooling to room temperature, 1000 g of toluene was added, and the organic layer was washed six times with 300 g of pure water. Subsequently, the organic layer was evaporated under reduced pressure to dryness. To the residue, 300 g of THF was added to form a homogeneous solution. Thereafter, the polymer was reprecipitated with 1000 g of methanol. The precipitated polymer was separated by filtration, washed twice with 600 g of methanol, and collected. The collected polymer was vacuum dried at 70° C. Thus, (A3) was obtained. The weight-average molecular weight (Mw) and dispersity (Mw/Mn) thereof were determined by GPC. The results were Mw=2040 and Mw/Mn=2.13.

Synthesis Example 4

Under a nitrogen atmosphere, a homogeneous solution with an inner temperature of 70° C. was prepared from 50.0 g of Compound (B3), 37.4 g of Compound (C4), 2.2 g of 3-mercaptopropionic acid, and 400 g of 1,2-dichloroethane. Then, 19.5 g of methanesulfonic acid was slowly added thereto for the reaction with an inner temperature of 70° C. for 24 hours. After cooling to room temperature, 1000 g of toluene was added, and the organic layer was washed six times with 300 g of pure water. Subsequently, the organic layer was evaporated under reduced pressure to dryness. To the residue, 300 g of THF was added to form a homogeneous solution. Thereafter, the polymer was reprecipitated with 1000 g of methanol. The precipitated polymer was separated by filtration, washed twice with 600 g of methanol, and collected. The collected polymer was vacuum dried at 70° C. Thus, (A4) was obtained. The weight-average molecular weight (Mw) and dispersity (Mw/Mn) thereof were determined by GPC. The results were Mw=2640 and Mw/Mn=2.45.

Synthesis Example 5

Under a nitrogen atmosphere, a suspension with an inner temperature of 50° C. was prepared from 31.5 g of Compound (B2), 50.0 g of Compound (C5), and 400 g of 1,2-dichloroethane. Then, 18.7 g of methanesulfonic acid was slowly added thereto. After confirming that the heat generation ended, the inner temperature was raised to 70° C. for the reaction for 8 hours. After cooling to room temperature, 1000 g of toluene was added, and the organic layer was washed six times with 300 g of pure water. Subsequently, the organic layer was evaporated under reduced pressure to dryness. To the residue, 300 g of THF was added to form a homogeneous solution. Thereafter, the polymer was reprecipitated with 1000 g of methanol. The precipitated polymer was separated by filtration, washed twice with 600 g of methanol, and collected. The collected polymer was vacuum dried at 70° C. Thus, (A5) was obtained. The weight-average molecular weight (Mw) and dispersity (Mw/Mn) thereof were determined by GPC. The results were Mw=2280 and Mw/Mn=1.85.

Synthesis Example 6

Under a nitrogen atmosphere, a homogeneous solution with an inner temperature of 50° C. was prepared from 26.4 g of Compound (B4), 50.0 g of Compound (C6), and 400 g of 1,2-dichloroethane. Then, 15.2 g of methanesulfonic acid was slowly added thereto. After confirming that the heat generation ended, the inner temperature was raised to 70° C. for the reaction for 8 hours. After cooling to room temperature, 1000 g of toluene was added, and the organic layer was washed six times with 300 g of pure water. Subsequently, the organic layer was evaporated under reduced pressure to dryness. To the residue, 300 g of THF was added to form a homogeneous solution. Thereafter, the polymer was reprecipitated with 1000 g of methanol. The precipitated polymer was separated by filtration, washed twice with 600 g of methanol, and collected. The collected polymer was vacuum dried at 70° C. Thus, (A6) was obtained. The weight-average molecular weight (Mw) and dispersity (Mw/Mn) thereof were determined by GPC. The results were Mw=2480 and Mw/Mn=2.08.

Synthesis Example 7

Under a nitrogen atmosphere, a homogeneous solution with an inner temperature of 50° C. was prepared from 44.5 g of Compound (B5), 50.0 g of Compound (C7), and 400 g of 1,2-dichloroethane. Then, 19.8 g of methanesulfonic acid was slowly added thereto. After confirming that the heat generation ended, the inner temperature was raised to 70° C. for the reaction for 8 hours. After cooling to room temperature, 1000 g of toluene was added, and the organic layer was washed six times with 300 g of pure water. Subsequently, the organic layer was evaporated under reduced pressure to dryness. To the residue, 300 g of THF was added to form a homogeneous solution. Thereafter, the polymer was reprecipitated with 1000 g of methanol. The precipitated polymer was separated by filtration, washed twice with 600 g of methanol, and collected. The collected polymer was vacuum dried at 70° C. Thus, (A7) was obtained. The weight-average molecular weight (Mw) and dispersity (Mw/Mn) thereof were determined by GPC. The results were Mw=2810 and Mw/Mn=2.28.

Synthesis Example 8

Under a nitrogen atmosphere, a homogeneous dispersion with an inner temperature of 50° C. was prepared from 15.0 g of Polymer (A3) synthesized in Synthesis Example 3, 0.8 g of tetrabutylammonium iodide, 14.6 g of a 25% sodium hydroxide aqueous solution, and 120 g of toluene. Then, 7.1 g of Compound (C8) was added thereto for the reaction with an inner temperature of 50° C. for 24 hours. After cooling to room temperature, 200 g of toluene was added, and the aqueous layer was removed. Further, the organic layer was washed twice with 60 g of a 3.0% nitric acid aqueous solution and five times with 60 g of pure water. The organic layer was evaporated under reduced pressure to dryness. To the residue, 80 g of THF was added, and the polymer was reprecipitated with 300 g of methanol. The precipitated polymer was separated by filtration, washed twice with 200 g of methanol, and collected. The collected polymer was vacuum dried at 70° C. Thus, (A8) was obtained. The weight-average molecular weight (Mw) and dispersity (Mw/Mn) thereof were determined by GPC. The results were Mw=2740 and Mw/Mn=2.08.

Synthesis Example 9

Under a nitrogen atmosphere, a homogeneous dispersion with an inner temperature of 50° C. was prepared from 15.0 g of Polymer (A3) synthesized in Synthesis Example 3, 0.8 g of tetrabutylammonium iodide, 14.6 g of a 25% sodium hydroxide aqueous solution, and 120 g of toluene. Then, 8.6 g of Compound (C2) was added thereto for the reaction with an inner temperature of 50° C. for 24 hours. After cooling to room temperature, 200 g of toluene was added, and the aqueous layer was removed. Further, the organic layer was washed twice with 60 g of a 3.0% nitric acid aqueous solution and five times with 60 g of pure water. The organic layer was evaporated under reduced pressure to dryness. To the residue, 80 g of THF was added, and the polymer was reprecipitated with 300 g of methanol. The precipitated polymer was separated by filtration, washed twice with 200 g of methanol, and collected. The collected polymer was vacuum dried at 70° C. Thus, (A9) was obtained. The weight-average molecular weight (Mw) and dispersity (Mw/Mn) thereof were determined by GPC. The results were Mw=2900 and Mw/Mn=2.12.

Synthesis Example 10

Under a nitrogen atmosphere, a homogeneous dispersion with an inner temperature of 50° C. was prepared from 15.0 g of Polymer (A3) synthesized in Synthesis Example 3, 0.8 g of tetrabutylammonium iodide, 14.6 g of a 25% sodium hydroxide aqueous solution, and 120 g of toluene. Then, 3.2 g of Compound (C9) was added thereto for the reaction with an inner temperature of 50° C. for 12 hours. Subsequently, 5.7 g of Compound (C8) was further added for the reaction for 24 hours. After cooling to room temperature, 200 g of toluene was added, and the aqueous layer was removed. Further, the organic layer was washed twice with 60 g of a 3.0% nitric acid aqueous solution and five times with 60 g of pure water. The organic layer was evaporated under reduced pressure to dryness. To the residue, 80 g of THF was added, and the polymer was reprecipitated with 300 g of methanol. The precipitated polymer was separated by filtration, washed twice with 200 g of methanol, and collected. The collected polymer was vacuum dried at 70° C. Thus, (A10) was obtained. The weight-average molecular weight (Mw) and dispersity (Mw/Mn) thereof were determined by GPC. The results were Mw=3050 and Mw/Mn=2.23.

Synthesis Example 11

Under a nitrogen atmosphere, a homogeneous dispersion with an inner temperature of 50° C. was prepared from 15.0 g of Polymer (A5) synthesized in Synthesis Example 5, 0.4 g of tetrabutylammonium iodide, 6.9 g of a 25% sodium hydroxide aqueous solution, and 100 g of toluene. Then, 5.3 g of Compound (C10) was added for the reaction with an inner temperature of 50° C. for 24 hours. After cooling to room temperature, 200 g of toluene was added, and the aqueous layer was removed. Further, the organic layer was washed twice with 60 g of a 3.0% nitric acid aqueous solution and five times with 60 g of pure water. The organic layer was evaporated under reduced pressure to dryness. To the residue, 80 g of THF was added, and the polymer was reprecipitated with 300 g of methanol. The precipitated polymer was separated by filtration, washed twice with 200 g of methanol, and collected. The collected polymer was vacuum dried at 70° C. Thus, (A11) was obtained. The weight-average molecular weight (Mw) and dispersity (Mw/Mn) thereof were determined by GPC. The results were Mw=2900 and Mw/Mn=1.81.

Synthesis Example 12

Under a nitrogen atmosphere, a homogeneous dispersion with an inner temperature of 50° C. was prepared from 15.0 g of Polymer (A5) synthesized in Synthesis Example 5, 0.4 g of tetrabutylammonium iodide, 6.9 g of a 25% sodium hydroxide aqueous solution, and 100 g of toluene. Then, 3.4 g of Compound (C11) was added thereto for the reaction with an inner temperature of 50° C. for 24 hours. After cooling to room temperature, 200 g of toluene was added, and the aqueous layer was removed. Further, the organic layer was washed twice with 60 g of a 3.0% nitric acid aqueous solution and five times with 60 g of pure water. The organic layer was evaporated under reduced pressure to dryness. To the residue, 80 g of THF was added, and the polymer was reprecipitated with 300 g of methanol. The precipitated polymer was separated by filtration, washed twice with 200 g of methanol, and collected. The collected polymer was vacuum dried at 70° C. Thus, (A12) was obtained. The weight-average molecular weight (Mw) and dispersity (Mw/Mn) thereof were determined by GPC. The results were Mw=2650 and Mw/Mn=1.90.

Comparative Synthesis Example 1

Under a nitrogen atmosphere, 18.0 g of 9-fluorenone was added to 12.8 g of naphthalene, and the temperature was raised to 230° C. for the reaction for 8 hours. Immediately after the reaction started, 0.25 ml of methanesulfonic acid was added to the reaction solution once every hour, i.e., eight times in total. After cooling to room temperature, 40 g of toluene was added to the reaction solution, the resultant was washed six times with pure water, and the organic layer was evaporated under reduced pressure to dryness. To the residue, 100 g of THF (tetrahydrofuran) was added to form a homogeneous solution, followed by crystallization with 300 g of methanol. The precipitated crystal was separated by filtration, washed twice with 200 g of methanol, and collected. The collected crystal was vacuum dried at 70° C. Thus, (R1) was obtained. The weight-average molecular weight (Mw) and dispersity (Mw/Mn) thereof were determined by GPC. The results were Mw=2130 and Mw/Mn=2.61.

Comparative Synthesis Example 2

Under a nitrogen atmosphere, 100 g of m-xylene was added to 100 g of 2-acetylfluorene, and the temperature was raised to 110° C. To the resulting homogeneous solution, 16.7 g of dodecylbenzenesulfonic acid was added, and the temperature was raised to 140° C. for the reaction for 16 hours. After completion of the reaction, the reaction solution was diluted with 400 g of m-xylene and then cooled to 50° C. Subsequently, the reaction solution was added dropwise to 2500 g of methanol for crystallization. The precipitated crystal was separated by filtration, washed twice with 500 g of methanol, and collected. The collected crystal was vacuum dried at 70° C. Thus, (R2) was obtained. The weight-average molecular weight (Mw) and dispersity (Mw/Mn) thereof were determined by GPC. The results were Mw=620 and Mw/Mn=1.03.

Comparative Synthesis Example 3

Under a nitrogen atmosphere, 10.0 g of Compound (R2) synthesized in Comparative Synthesis Example 2, 18.8 g of propargyl bromide, and 50 g of toluene were added and stirred together. Then, 25.2 g of a 50% sodium hydroxide aqueous solution and 1.7 g of tetrabutylammonium bromide were added thereto for the reaction at 90° C. for 12 hours. After cooling to room temperature, 100 g of toluene was added to the reaction solution, and the resultant was washed six times with pure water. The organic layer was evaporated under reduced pressure to dryness. To the residue, 60 g of THF (tetrahydrofuran) was added to form a homogeneous solution, followed by crystallization with 300 g of methanol. The precipitated crystal was separated by filtration, washed twice with 200 g of methanol, and collected. The collected crystal was vacuum dried at 70° C. Thus, (R3) was obtained. The weight-average molecular weight (Mw) and dispersity (Mw/Mn) thereof were determined by GPC. The results were Mw=820 and Mw/Mn=1.05.

Comparative Synthesis Example 4

Under a nitrogen atmosphere, 10.0 g of Compound (R2) synthesized in Comparative Synthesis Example 2, 11.0 g of Compound (C8), and 80 g of tetrahydrofuran were added and stirred together. Then, 33.6 g of a 25% sodium hydroxide aqueous solution and 1.7 g of tetrabutylammonium bromide were added thereto for the reaction at 50° C. for 12 hours. After cooling to room temperature, 100 g of toluene was added to the reaction solution, and the resultant was washed six times with pure water. The organic layer was evaporated under reduced pressure to dryness. To the residue, 60 g of THF (tetrahydrofuran) was added to form a homogeneous solution, followed by crystallization with 300 g of methanol. The precipitated crystal was separated by filtration, washed twice with 200 g of methanol, and collected. The collected crystal was vacuum dried at 70° C. Thus, (R4) was obtained. The weight-average molecular weight (Mw) and dispersity (Mw/Mn) thereof were determined by GPC. The results were Mw=960 and Mw/Mn=1.04.

Table 1 shows a list of the structural formulae of Polymers (A1) to (A12) used in Examples and Polymers (R1) to (R4) used in Comparative Examples as well as the results of Mw and Mw/Mn.

TABLE 1 Synthesis Mw/ Example Compound Mw Mn 1

2200 2.48 (A1) 2

3440 3.23 (A2) 3

2040 2.13 (A3) 4

2640 2.45 (A4) 5

2280 1.85 (A5) 6

2480 2.08 (A6) 7

2810 2.28 (A7) 8

2740 2.08 (A8) 9

2900 2.12 (A9) 10

3050 2.23 (A10) 11

2900 1.81 (A11) 12

2650 1.90 (A12) Comparative Synthesis Example 1

2130 2.61 (R1) Comparative Synthesis Example 2

620 1.03 (R2) Comparative Synthesis Example 3

820 1.05 (R3) Comparative Synthesis Example 4

960 1.04 (R4)

Preparation of Compositions (UDL-1 to -16, Comparative UDL-1 to -5) for Forming Organic Film

Polymers (A1) to (A12) and Compounds (R1) to (R4) for Comparative Examples described above were dissolved in proportions shown in Table 2 using propylene glycol monomethyl ether acetate (PGMEA) or cyclohexanone (CyHO), both of which contained 0.1 mass % FC-4430 (manufactured by Sumitomo 3M Ltd.), and optionally using (S1) 1,6-diacetoxyhexane (boiling point: 260° C.) and (S2) tripropylene glycol monomethyl ether (boiling point: 242° C.) as high-boiling-point solvents. The solutions were filtered through a 0.1-μm filter made of a fluorinated resin to prepare compositions (UDL-1 to -16, Comparative UDL-1 to -5) for forming an organic film. Note that an acid generator (AG) and a crosslinking agent (XL) shown by the following formulae were used in Comparative UDL-2.

TABLE 2 High- Polymer Polymer boiling- Composition (1) (2) point for forming (parts (parts Additive solvent Solvent organic by by (parts (parts (parts by film mass) mass) by mass) by mass) mass) UDL-1 A1(10) — — — CyHO(90) UDL-2 A2(10) — — — CyHO(90) UDL-3 A3(10) — — — CyHO(90) UDL-4 A4(10) — — — PGMEA(90) UDL-5 A5(10) — — — PGMEA(90) UDL-6 A6(10) — — — PGMEA(90) UDL-7 A7(10) — — — PGMEA(90) UDL-8 A8(10) — — — PGMEA(45) CyHO(45) UDL-9 A9(10) — — — PGMEA(45) CyHO(45) UDL-10 A10(10) — — — PGMEA(45) CyHO(45) UDL-11 A11(10) — — — PGMEA(90) UDL-12 A12(10) — — — PGMEA(90) UDL-13 A3(5) A4(5) — — PGMEA(45) CyHO(45) UDL-14 A3(5) A11(5) — — PGMEA(45) CyHO(45) UDL-15 A8(10) — — S1(10) PGMEA(45) CyHO(45) UDL-16 A11(10) — — S2(10) PGMEA(80) Comparative R1(10) — — — CyHO(90) UDL-1 Comparative R1(10) — AG(0.5) — CyHO(90) UDL-2 XL(0.5) Comparative R2(10) — — — CyHO(90) UDL-3 Comparative R3(10) — — — PGMEA(70) UDL-4 CyHO(30) Comparative R4(10) — — — PGMEA(90) UDL-5

Examples 1-1 to 1-16, Comparative Examples 1-1 to 1-5 (Solvent Resistance Measurement)

UDL-1 to -16 and Comparative UDL-1 to -5 were each applied onto a silicon substrate and baked in the atmosphere at 350° C. for 60 seconds. Then, the film thickness was measured. A PGMEA solvent was dispensed on the film and allowed to stand for 30 seconds. The resultant was spin dried and baked at 100° C. for 60 seconds to evaporate the PGMEA. The film thickness was measured to find the film thicknesses before and after the PGMEA treatment. The film thickness after the film formation and the film thickness after the PGMEA treatment were used to determine a film remaining ratio. Table 3 shows the result.

TABLE 3 Film Film thickness Composition thickness after for forming after film PGMEA organic formation: treatment: b/a × 100 film a (Å) b (Å) (%) Example 1-1 UDL-1 1994 1989 99.7 Example 1-2 UDL-2 1986 1981 99.7 Example 1-3 UDL-3 2006 2003 99.9 Example 1-4 UDL-4 1992 1982 99.5 Example 1-5 UDL-5 1999 1992 99.6 Example 1-6 UDL-6 1990 1982 99.6 Example 1-7 UDL-7 1989 1979 99.5 Example 1-8 UDL-8 1989 1983 99.7 Example 1-9 UDL-9 1990 1980 99.5 Example 1-10 UDL-10 2001 1995 99.7 Example 1-11 UDL-11 2007 2000 99.7 Example 1-12 UDL-12 2002 1993 99.6 Example 1-13 UDL-13 2011 2007 99.8 Example 1-14 UDL-14 1999 1994 99.7 Example 1-15 UDL-15 1988 1986 99.9 Example 1-16 UDL-16 2014 2010 99.8 Comparative Comparative 1998 1370 68.6 Example 1-1 UDL-1 Comparative Comparative 2000 1981 99.1 Example 1-2 UDL-2 Comparative Comparative 2007 1999 99.6 Example 1-3 UDL-3 Comparative Comparative 2014 2008 99.7 Example 1-4 UDL-4 Comparative Comparative 1990 1982 99.6 Example 1-5 UDL-5

As shown in Table 3, the film remaining percentages after the PGMEA treatment on the organic films (Examples 1-1 to 1-16) using the inventive polymers were 99% or more. This indicates that the crosslinking reaction took place by heating, and sufficient solvent resistance was exhibited. In contrast, when Polymer (R1) was used alone (Comparative UDL-1), the polymer alone had no crosslinkable moiety and did not exhibit solvent resistance. In order for solvent resistance to be exhibited, the acid generator and the crosslinking agent need to be added. These results indicate that the partial structures of the inventive polymers effectively function as thermal-crosslinking groups. It was confirmed that when the compounds having crosslinkable structures were used (Comparative Examples 1-3 to 1-5), solvent resistance was exhibited.

Examples 2-1 to 2-16, Comparative Examples 2-1 to 2-5 (Hardness Measurement)

UDL-1 to -16 and Comparative UDL-1 to -5 were each applied onto a silicon substrate and baked in the atmosphere at 350° C. for 60 seconds to form an organic film having a film thickness of 200 nm. Such organic films were subjected to a nano-indentation test with a SA2 nanoindenter instrument manufactured by TOYO Corporation, and the hardnesses of the organic films were measured. Table 4 shows the result.

TABLE 4 Composition for forming Hardness organic film (GPa) Example 2-1 UDL-1 0.61 Example 2-2 UDL-2 0.62 Example 2-3 UDL-3 0.68 Example 2-4 UDL-4 0.69 Example 2-5 UDL-5 0.67 Example 2-6 UDL-6 0.64 Example 2-7 UDL-7 0.71 Example 2-8 UDL-8 0.72 Example 2-9 UDL-9 0.64 Example 2-10 UDL-10 0.71 Example 2-11 UDL-11 0.72 Example 2-12 UDL-12 0.69 Example 2-13 UDL-13 0.68 Example 2-14 UDL-14 0.67 Example 2-15 UDL-15 0.73 Example 2-16 UDL-16 0.66 Comparative Comparative 0.45 Example 2-1 UDL-1 Comparative Comparative 0.48 Example 2-2 UDL-2 Comparative Comparative 0.63 Example 2-3 UDL-3 Comparative Comparative 0.65 Example 2-4 UDL-4 Comparative Comparative 0.66 Example 2-5 UDL-5

As shown in Table 4, the hardnesses of Examples 2-1 to 2-16 were higher than those of Comparative Examples 2-1 and 2-2. This verified that the inventive polymers are capable of forming finer and stronger films than those formed from Polymer (R1) used in Comparative UDL-1 and -2. This is because the inventive polymers are thermosetting. Hence, the cured films obtained therefrom can form fine films constituted of only condensed aromatic rings with high carbon density, consequently exhibiting high hardnesses. In contrast, Polymer (R1) used in Comparative Examples has high carbon density, but the polymer itself is not thermosetting. The resulting films did not have high hardness values. Moreover, although Polymer (R1) can exhibit solvent resistance by using the crosslinking agent, the crosslinking agent impairs the carbon density of the polymer. As a result, the cured films did not have high hardness. When the compounds having crosslinkable structures were used (Comparative Examples 2-3 to 2-5), sufficient crosslinking was possible as demonstrated from the result of the solvent resistance test, and Comparative Examples 2-3 to 2-5 were found to have hardnesses equivalent to those of the inventive polymers.

Examples 3-1 to 3-16, Comparative Examples 3-1 to 3-5 (Etching Test)

[Etching Test with CF₄/CHF₃-Based Gas]

UDL-1 to -16 and Comparative UDL-1 to -5 were each applied onto a silicon substrate and baked in the atmosphere at 350° C. for 60 seconds to form an organic film having a film thickness of 200 nm. Then, an etching test was conducted with a CF₄/CHF₃-based gas under the following conditions. In this case, a dry etching apparatus TE-8500 manufactured by Tokyo Electron Limited was used to find a film thickness difference of each organic film before and after the etching. Table 5 shows the result.

The etching conditions were as follows.

Chamber pressure 40.0 Pa RF power 1,000 W CHF₃ gas flow rate 10 ml/min CF₄ gas flow rate 100 ml/min He gas flow rate 200 ml/min Time 20 sec

TABLE 5 Etching test with Etching test with CF₄/CHF₃— based gas O₂-based gas Film Film reduction reduction Film ratio with Film ratio with Composition thickness Comparative thickness Comparative for forming reduction Example 2-1 reduction Example 2-1 organic film amount (A) taken as 100% amount (A) taken as 100% Example 3-1 UDL-1 876  98% 1242  98% Example 3-2 UDL-2 869  97% 1226  97% Example 3-3 UDL-3 839  93% 1187  93% Example 3-4 UDL-4 834  93% 1180  93% Example 3-5 UDL-5 832  93% 1175  93% Example 3-6 UDL-6 851  95% 1200  95% Example 3-7 UDL-7 838  93% 1187  94% Example 3-8 UDL-8 839  93% 1180  93% Example 3-9 UDL-9 838  93% 1187  93% Example 3-10 UDL-10 836  93% 1183  93% Example 3-11 UDL-11 821  91% 1166  92% Example 3-12 UDL-12 841  94% 1184  93% Example 3-13 UDL-13 837  93% 1184  93% Example 3-14 UDL-14 830  92% 1176  93% Example 3-15 UDL-15 838  93% 1181  93% Example 3-16 UDL-16 820  91% 1164  92% Comparative Comparative 898 100% 1270 100% Example 3-1 UDL-1 Comparative Comparative 987 110% 1413 111% Example 3-2 UDL-2 Comparative Comparative 898 100% 1270 100% Example 3-3 UDL-3 Comparative Comparative 898 100% 1270 100% Example 3-4 UDL-4 Comparative Comparative 987 110% 1413 111% Example 3-5 UDL-5

Table 5 shows the film reduction ratio in each Example and Comparative Example, given that the thickness of the Comparative UDL-1 film reduced by the etching with CF₄/CHF₃-based gas is taken as 100. The smaller the ratio, the more excellent the etching resistance.

[Etching Test with O₂-Based Gas]

UDL-1 to -16 and Comparative UDL-1 to -5 were each applied onto a silicon substrate and baked in the atmosphere at 350° C. for 60 seconds to form an organic film having a film thickness of 200 nm. An etching test was conducted with an O₂-based gas under the following conditions. In this case, a dry etching apparatus TE-8500 manufactured by Tokyo Electron Limited was used to find a film thickness difference of each polymer film before and after the etching. Table 5 also shows this result.

The etching conditions were as follows.

Chamber pressure 40.0 Pa RF power 100 W O₂ gas flow rate 30 ml/min N₂ gas flow rate 70 ml/min Time 60 sec

As in the case of the etching test with a CF₄/CHF₃-based gas, Table 5 shows the film reduction ratio in each Example and Comparative Example, given that the thickness of the Comparative UDL-1 film reduced by the etching with O₂-based gas is taken as 100. The smaller the ratio, the more excellent the etching resistance.

As shown in Table 5, the comparison between Examples 3-1 to 3-16 and Comparative Examples 3-1, 3-2 shows that, in both the etching tests with CF₄/CHF₃-based gas and O₂-based gas, the reduction amounts after the etching of the organic films in Examples 3-1 to 3-16 were smaller than the film reduction amounts after the etching of the Comparative UDL-1 and -2 organic films. This indicates that the organic films excellent in etching resistance were formed in Examples 3-1 to 3-16. The comparison between Comparative Examples 3-1 and 3-2 revealed that, in Comparative Example 3-2 in which the cured film was formed using the crosslinking agent, the addition of the crosslinking agent decreased the carbon content of the organic film and consequently impaired the etching resistance by approximately 10%. Further, the comparison between Examples 3-1 to 3-16 using the inventive polymers and Comparative Example 3-1 using Comparative Polymer (R1) revealed that the organic films according to the present invention had excellent etching resistance in comparison with Comparative Example 3-1. This is because fine cured films were formed by the thermal crosslinking in Examples 3-1 to 3-16 using the inventive polymers as suggested from the hardness measurement result shown in Table 4. In the present invention, Examples 3-3 to 3-16 each of which contained a fluorene structure(s) at the divalent linking group in the repeating unit resulted in more excellent etching resistance than Examples 3-1 and 3-2.

Examples 4-1 to 4-16, Comparative Examples 4-1 to 4-5 (Pattern Etching Test)

UDL-1 to -16 and Comparative UDL-1 to -5 were each applied onto a Si wafer substrate having a diameter of 300 mm on which a SiO₂ film with a film thickness of 200 nm had been formed. Then, a resist underlayer film was formed to have a film thickness of 200 nm after baking in the atmosphere at 350° C. for 60 seconds. A silicon-containing resist middle layer material (SOG-1) was applied onto the resist underlayer film and baked at 220° C. for 60 seconds to form a resist middle layer film having a film thickness of 35 nm. A resist upper layer film material (SL resist for ArF) was applied thereon and baked at 105° C. for 60 seconds to form a resist upper layer film having a film thickness of 100 nm. A liquid immersion top coat material (TC-1) was applied onto the resist upper layer film and baked at 90° C. for 60 seconds to form a top coat having a film thickness of 50 nm.

The resist upper layer film material (SL resist for ArF) was prepared by: dissolving 100 parts by mass of a polymer (RP1) shown by the following formula, 6.6 parts by mass of acid generator (PAG1) shown by the following formula, and 0.8 parts by mass of a basic compound (Amine1) shown by the following formula in 2500 parts by mass of PGMEA containing 0.1 mass % FC-430 (manufactured by Sumitomo 3M Ltd.); and filtering the solution through a 0.1-μm filter made of a fluorinated resin.

The liquid immersion top coat material (TC-1) was prepared by: dissolving 100 parts by mass of a top coat polymer (PP1) shown by the following formula in an organic solvent consisting of 2700 parts by mass of diisoamyl ether and 270 parts by mass of 2-methyl-1-butanol; and filtering the solution through a 0.1-μm filter made of a fluorinated resin.

The silicon-containing resist middle layer material (SOG-1) was prepared by: dissolving 100 parts by mass of an ArF silicon-containing middle layer film polymer (SiP1) shown by the following formula and 1 part by mass of a crosslinking catalyst (CAT1) shown by the following formula in 4000 parts by mass of PGMEA containing 0.1 mass % FC-4430 (manufactured by Sumitomo 3M Ltd.); and filtering the solution through a filter having a pore size of 0.1 μm and made of a fluorinated resin.

Next, the resulting substrate was exposed to light at various exposure levels with an ArF liquid immersion exposure apparatus (NSR-S610C manufactured by Nikon Corporation, NA: 1.30, σ: 0.98/0.65, 35° s-polarized dipole illumination, 6% halftone phase shift mask), baked at 100° C. for 60 seconds (PEB), and developed with a 2.38 mass % tetramethylammonium hydroxide (TMAH) aqueous solution for 30 seconds. Thus, a positive line and space pattern was obtained with the resist line width ranging from 50 nm to 30 nm at a pitch of 100 nm.

Then, dry-etching processing with an etching apparatus Telius manufactured by Tokyo Electron Limited was performed successively as follows. The silicon-containing middle layer was processed using the resist pattern as a mask; the underlayer film was processed using the silicon-containing middle layer as a mask; and the SiO₂ film was processed using the underlayer film as a mask.

The etching conditions were as follows. Conditions for transferring the resist pattern to the SOG film:

Chamber pressure 10.0 Pa RF power 1,500 W CF₄ gas flow rate 15 sccm O₂ gas flow rate 75 sccm Time 15 sec Conditions for transferring the SOG film to the underlayer film:

Chamber pressure 2.0 Pa RF power 500 W Ar gas flow rate 75 sccm O₂ gas flow rate 45 sccm Time 120 sec Transferring conditions to the SiO₂ film:

Chamber pressure 2.0 Pa RF power 2,200 W C₅F₁₂ gas flow rate 20 sccm C₂F₆ gas flow rate 10 sccm Ar gas flow rate 300 sccm O₂ gas flow rate 60 sccm Time 90 sec

The pattern cross sections were observed with an electron microscope (S-4700) manufactured by Hitachi, Ltd. The profiles were compared and summarized in Table 6.

TABLE 6 Minimum dimension (nm) without pattern Profile after Profile after twisting etching for etching for Profile after after etching Composition Pattern transferring transferring etching for for for forming profile after to middle to underlayer transferring transferring organic film development layer film to substrate to substrate Example 4-1 UDL-1  vertical vertical vertical vertical 33 profile profile profile profile Example 4-2 UDL-2  vertical vertical vertical vertical 33 profile profile profile profile Example 4-3 UDL-3  vertical vertical vertical vertical 30 profile profile profile profile Example 4-4 UDL-4  vertical vertical vertical vertical 29 profile profile profile profile Example 4-5 UDL-5  vertical vertical vertical vertical 30 profile profile profile profile Example 4-6 UDL-6  vertical vertical vertical vertical 32 profile profile profile profile Example 4-7 UDL-7  vertical vertical vertical vertical 28 profile profile profile profile Example 4-8 UDL-8  vertical vertical vertical vertical 28 profile profile profile profile Example 4-9 UDL-9  vertical vertical vertical vertical 32 profile profile profile profile Example 4-10 UDL-10 vertical vertical vertical vertical 28 profile profile profile profile Example 4-11 UDL-11 vertical vertical vertical vertical 28 profile profile profile profile Example 4-12 UDL-12 vertical vertical vertical vertical 29 profile profile profile profile Example 4-13 UDL-13 vertical vertical vertical vertical 30 profile profile profile profile Example 4-14 UDL-14 vertical vertical vertical vertical 30 profile profile profile profile Example 4-15 UDL-15 vertical vertical vertical vertical 28 profile profile profile profile Example 4-16 UDL-16 vertical vertical vertical vertical 31 profile profile profile profile Comparative Comparative no pattern — — — — Example 4-1 UDL-1 Comparative Comparative vertical vertical vertical vertical 42 Example 4-2 UDL-2 profile profile profile profile Comparative Comparative vertical vertical vertical vertical 32 Example 4-3 UDL-3 profile profile profile profile Comparative Comparative vertical vertical vertical vertical 31 Example 4-4 UDL-4 profile profile profile profile Comparative Comparative vertical vertical vertical vertical 31 Example 4-5 UDL-5 profile profile profile profile

The results of Examples 4-1 to 4-16 revealed that when UDL-1 to -16 were used as resist underlayer film of the three-layer resists for liquid immersion lithography, the resist profiles after the development were favorable in the pattern profile evaluation. This indicates useful effect as an antireflective film. In contrast, Comparative UDL-1 used in Comparative Example 4-1 is not thermosetting, and did not attain solvent resistance. Thus, when the silicon-containing resist middle layer material (SOG-1) was applied, the film was dissolved, so that no pattern was formed.

Regarding the pattern profiles after the etching in Examples 4-1 to 4-16, the resist profiles after the development and the profiles of the underlayer films after oxygen etching and substrate-processing etching were all favorable. In accordance with the resist line width formed by the light exposure, the pattern dimension transferred to the substrate was also changed. In Comparative Example 4-2, the pattern was twisted at the line width of approximately 40 nm. In contrast, in Examples 4-1 to 4-16 using the inventive polymers, no twisting occurred even if the pattern dimension was 35 nm or less. These revealed that the inventive polymers enable high twisting resistance. It is understood that as in the case of the inventive polymers, when an organic film capable of forming a fine and high-strength film having a hardness exceeding 0.60 GPa is used as a resist underlayer film, high twisting resistance is obtained.

Examples 5-1 to 5-16 (Filling Property)

On a stepped SiO₂ substrate which was a SiO₂ substrate having a dense hole pattern with a thickness of 500 nm and a diameter of 160 nm formed thereon, a resist underlayer film was formed by applying one of UDL-1 to -16 under such conditions that the film with a thickness of 80 nm was formed on a flat substrate by baking at 350° C. for 60 seconds. Each substrate having such a resist underlayer film formed thereon was split and observed with a scanning electron microscope (SEM) to check whether the resist underlayer film was filled to the bottoms of the holes. Table 7 shows the result.

TABLE 7 Composition for forming organic film Filling property Example 5-1 UDL-1 favorably filled to the bottoms of holes Example 5-2 UDL-2 favorably filled to the bottoms of holes Example 5-3 UDL-3 favorably filled to the bottoms of holes Example 5-4 UDL-4 favorably filled to the bottoms of holes Example 5-5 UDL-5 favorably filled to the bottoms of holes Example 5-6 UDL-6 favorably filled to the bottoms of holes Example 5-7 UDL-7 favorably filled to the bottoms of holes Example 5-8 UDL-8 favorably filled to the bottoms of holes Example 5-9 UDL-9 favorably filled to the bottoms of holes Example 5-10 UDL-10 favorably filled to the bottoms of holes Example 5-11 UDL-11 favorably filled to the bottoms of holes Example 5-12 UDL-12 favorably filled to the bottoms of holes Example 5-13 UDL-13 favorably filled to the bottoms of holes Example 5-14 UDL-14 favorably filled to the bottoms of holes Example 5-15 UDL-15 favorably filled to the bottoms of holes Example 5-16 UDL-16 favorably filled to the bottoms of holes

As shown in Table 7, in all of Examples 5-1 to 5-16 in which the resist underlayer films were formed by using UDL-1 to UDL-16 of the present invention, the holes were favorably filled to the bottoms. This indicates that even when a substrate to be processed has a step(s), sufficient filling property can be expected, and the compositions according to the present invention have useful properties as a resist underlayer film material for multilayer processes.

Examples 6-1 to 6-4, Comparative Example 6-1 and 6-2 (Planarizing Property)

Each composition (UDL-8, -11, -15, -16, Comparative UDL-1, -2) for forming an organic film was applied onto a SiO₂ wafer substrate having a giant isolated trench pattern (trench width: 10 μm, trench depth: 0.10 μm) and baked in the atmosphere at 350° C. for 60 seconds. Then, a step (delta in FIG. 2 ) between the trench portion and the non-trench portion of the organic film was observed with an atomic force microscope (AFM) NX10 manufactured by Park systems Corp. Table 8 shows the result. In this evaluation, the smaller the step, the more favorable the planarizing property. Note that, in this evaluation, a trench pattern having a depth of 0.10 μm was generally planarized using a composition for forming an organic film having a film thickness of approximately 0.2 μm. This is a strict evaluation condition to evaluate the planarizing property.

TABLE 8 Composition for forming organic film Step (nm) Example 6-1 UDL-8 70 Example 6-2 UDL-11 75 Example 6-3 UDL-15 60 Example 6-4 UDL-16 65 Comparative Comparative UDL-1 90 Example 6-1 Comparative Comparative UDL-2 90 Example 6-2

As shown in Table 8, the organic films obtained from the inventive compositions for forming an organic film had smaller steps between the trench and non-trench portions than those in Comparative Examples 6-1, 6-2. This verified that the inventive compositions are excellent in planarizing property. It is presumed that in Comparative Examples 6-1 and 6-2, the films are inferior in fineness and considerably shrunk by baking, therefore the film thickness difference between the upper portion and the lower portion of the step was emphasized by the baking, and the planarizing property was poor. Moreover, the comparison between Examples 6-3, 6-4 in which the high-boiling-point solvents were added and Examples 6-1, 6-2 without the high-boiling-point solvents shows that adding the high-boiling-point solvents improved the planarizing property.

Examples 7-1 to 7-16, Comparative Examples 7-1 to 7-3 (Sublimation Property)

Each composition (UDL-1 to -16, Comparative UDL-3 to -5) for forming an organic film was applied onto a Si substrate and baked in the atmosphere at 350° C. for 60 seconds. The number of particles with sizes of 0.3 μm and 0.5 μm, which were generated inside a hot plate oven during the baking, was measured with a particle counter KR-11A manufactured by RION Co., Ltd. Table 9 shows the measurement result.

TABLE 9 Composition for forming 0.3-μm 0.5-μm organic particles particles film (number) (number) Example 7-1 UDL-1  12  2 Example 7-2 UDL-2  8  2 Example 7-3 UDL-3  8  3 Example 7-4 UDL-4  10  2 Example 7-5 UDL-5  8  1 Example 7-6 UDL-6  5  1 Example 7-7 UDL-7  4  0 Example 7-8 UDL-8  3  0 Example 7-9 UDL-9  9  0 Example 7-10 UDL-10  7  2 Example 7-11 UDL-11  5  1 Example 7-12 UDL-12  8  2 Example 7-13 UDL-13  9  1 Example 7-14 UDL-14  7  1 Example 7-15 UDL-15  4  0 Example 7-16 UDL-16  6  0 Comparative Comparative 208 65 Example 7-1 UDL-3 Comparative Comparative 134 41 Example 7-2 UDL-4 Comparative Comparative 124 37 Example 7-3 UDL-5

As shown in Table 9, it is understood that in Examples 7-1 to 7-16 in which organic films were formed using UDL-1 to UDL-16 of the present invention, fewer particles were generated during the baking than in Comparative Examples 7-1 to 7-3. Although all the compounds used in these Examples and Comparative Examples have thermosetting properties, the inventive compositions for forming an organic film use the polymers which contain less low-molecular-weight component. Thus, the generation of sublimation product evaporated during baking was successfully suppressed.

Examples 8-1 to 8-16, Comparative Examples 8-1 to 8-3 (Coatability Test)

Each composition (UDL-1 to -16, Comparative UDL-3 to -5) for forming an organic film was applied onto each of a Bare-Si substrate, a substrate treated with hexamethyldisilazane (HMDS), and a substrate treated with SiON, which are shown in Table 10, and baked in the atmosphere at 350° C. for 60 seconds to form an organic film having a film thickness of 200 nm. The organic films thus formed were observed with an optical microscope (ECLIPSE L200 manufactured by Nikon INSTECH CO., LTD.) to check the coating abnormality. Table 10 shows the observation result.

TABLE 10 Composition for forming Bare-Si HMDS-treated SiON-treated organic film substrate substrate substrate Example 8-1 UDL-1 no no no abnormality abnormality abnormality Example 8-2 UDL-2 no no no abnormality abnormality abnormality Example 8-3 UDL-3 no no no abnormality abnormality abnormality Example 8-4 UDL-4 no no no abnormality abnormality abnormality Example 8-5 UDL-5 no no no abnormality abnormality abnormality Example 8-6 UDL-6 no no no abnormality abnormality abnormality Example 8-7 UDL-7 no no no abnormality abnormality abnormality Example 8-8 UDL-8 no no no abnormality abnormality abnormality Example 8-9 UDL-9 no no no abnormality abnormality abnormality Example 8-10 UDL-10 no no no abnormality abnormality abnormality Example 8-11 UDL-11 no no no abnormality abnormality abnormality Example 8-12 UDL-12 no no no abnormality abnormality abnormality Example 8-13 UDL-13 no no no abnormality abnormality abnormality Example 8-14 UDL-14 no no no abnormality abnormality abnormality Example 8-15 UDL-15 no no no abnormality abnormality abnormality Example 8-16 UDL-16 no no no abnormality abnormality abnormality Comparative Comparative no pinhole pinhole Example 8-1 UDL-3 abnormality defect defect Comparative Comparative no pinhole pinhole Example 8-2 UDL-4 abnormality defect defect Comparative Comparative no pinhole pinhole Example 8-3 UDL-5 abnormality defect defect

As shown in Table 10, in Examples 8-1 to 8-16 in which organic films were formed using UDL-1 to UDL-16 of the present invention, uniform organic films were successfully formed without coating abnormality regardless of the substrates. In contrast, in Comparative Examples 8-1 to 8-3, since the single-molecular compounds were used, agglomeration is likely to occur depending on the substrate, so that many pinhole-like coating defects which seemed splash were observed. It was demonstrated that the use of the inventive polymers enables the formation of uniform coating films without substrate dependency.

From the above, the inventive composition for forming an organic film enables high etching resistance and excellent twisting resistance during etching. The inventive composition is a quite useful material of an underlayer film for multilayer resist processes, particularly a three-layer resist process, for ultrafine and very precise patterning.

It should be noted that the present invention is not limited to the above-described embodiments. The embodiments are just examples, and any examples that have substantially the same feature and demonstrate the same functions and effects as those in the technical concept disclosed in claims of the present invention are included in the technical scope of the present invention. 

The invention claimed is:
 1. A composition for forming an organic film, comprising: an organic solvent; and a polymer containing a repeating unit shown by the following general formula (1A) as a partial structure:

wherein: AR₁ and AR₂ each represent a benzene ring or a naphthalene ring which optionally have a substituent; W₁ represents any in the following general formula (1B), and the polymer optionally contains two kinds of W₁ in combination:

wherein: each R₁ is any in the following general formula (1C),

and R₂ is any in the following general formula (1D),

and W₂ represents a divalent organic group having 1 to 80 carbon atoms.
 2. The composition for forming an organic film according to claim 1, wherein the polymer has a weight-average molecular weight of 1000 to
 5000. 3. The composition for forming an organic film according to claim 1, further comprising at least one of a surfactant and a plasticizer.
 4. A composition for forming an organic film, comprising: an organic solvent; and a polymer containing a repeating unit shown by the following general formula (1A) as a partial structure:

wherein: AR₁ and AR₂ each represent a benzene ring or a naphthalene ring which optionally have a substituent; W₁ represents any in the following general formula (1B), and the polymer optionally contains two or more kinds of W₁ in combination,

wherein: each R₁ represents a monovalent organic group having 1 to 10 carbon atoms and an unsaturated bond; and R₂ represents a monovalent organic group having 6 to 20 carbon atoms and one or more aromatic rings; and W₂ is any in the following general formula (1E),

wherein: AR₃ and AR₄ each represent a benzene ring or a naphthalene ring which optionally have a substituent; and W₃ represents a divalent organic group having 6 to 50 carbon atoms and one or more aromatic rings.
 5. The composition for forming an organic film according to claim 4, wherein the divalent organic group represented by W₃ in the general formula (1E) is any in the following general formula,


6. A composition for forming an organic film, comprising: a mixture of one or more organic solvents each having a boiling point of lower than 180° C. and one or more organic solvents each having a boiling point of 180° C. or higher; and a polymer containing a repeating unit shown by the following general formula (1A) as a partial structure,

wherein: AR₁ and AR₂ each represent a benzene ring or a naphthalene ring which optionally have a substituent; W₁ represents any in the following general formula (1B), and the polymer optionally contains two or more kinds of W₁ in combination,

wherein: each R₁ represents a monovalent organic group having 1 to 10 carbon atoms and an unsaturated bond; and R₂ represents a monovalent organic group having 6 to 20 carbon atoms and one or more aromatic rings; and W₂ represents a divalent organic group having 1 to 80 carbon atoms.
 7. A patterning process comprising the steps of: forming an organic film by using the composition for forming an organic film according to claim 1 on a body to be processed; forming a silicon-containing resist underlayer film by using a silicon-containing resist underlayer film material on the organic film; forming a resist upper layer film by using a photoresist composition on the silicon-containing resist underlayer film; forming a circuit pattern in the resist upper layer film; transferring the pattern to the silicon-containing resist underlayer film by etching using the resist upper layer film having the formed circuit pattern as a mask; transferring the pattern to the organic film by etching using the silicon-containing resist underlayer film having the transferred pattern as a mask; and forming the pattern in the body to be processed by etching using the organic film having the transferred pattern as a mask.
 8. A patterning process comprising the steps of: forming an organic film by using the composition for forming an organic film according to claim 1 on a body to be processed; forming a silicon-containing resist underlayer film by using a silicon-containing resist underlayer film material on the organic film; forming an organic antireflective coating (BARC) on the silicon-containing resist underlayer film; forming a resist upper layer film by using a photoresist composition on the BARC; forming a circuit pattern in the resist upper layer film; successively transferring the pattern to the BARC and the silicon-containing resist underlayer film by etching using the resist upper layer film having the formed circuit pattern as a mask; transferring the pattern to the organic film by etching using the silicon-containing resist underlayer film having the transferred pattern as a mask; and etching the body to be processed using the organic film having the transferred pattern as a mask to form the pattern in the body to be processed.
 9. A patterning process comprising the steps of: forming an organic film by using the composition for forming an organic film according to claim 1 on a body to be processed; forming an inorganic hard mask selected from a silicon oxide film, a silicon nitride film, and a silicon oxynitride film on the organic film; forming a resist upper layer film by using a photoresist composition on the inorganic hard mask; forming a circuit pattern in the resist upper layer film; transferring the pattern to the inorganic hard mask by etching using the resist upper layer film having the formed circuit pattern as a mask; transferring the pattern to the organic film by etching using the inorganic hard mask having the formed pattern as a mask; and etching the body to be processed using the organic film having the formed pattern as a mask to form the pattern in the body to be processed.
 10. A patterning process comprising the steps of: forming an organic film by using the composition for forming an organic film according to claim 1 on a body to be processed; forming an inorganic hard mask selected from a silicon oxide film, a silicon nitride film, and a silicon oxynitride film on the organic film; forming a BARC on the inorganic hard mask; forming a resist upper layer film by using a photoresist composition on the BARC; forming a circuit pattern in the resist upper layer film; successively transferring the pattern to the BARC and the inorganic hard mask by etching using the resist upper layer film having the formed circuit pattern as a mask; transferring the pattern to the organic film by etching using the inorganic hard mask having the formed pattern as a mask; and etching the body to be processed using the organic film having the formed pattern as a mask to form the pattern in the body to be processed.
 11. The patterning process according to claim 9, wherein the inorganic hard mask is formed by a CVD method or an ALD method.
 12. The patterning process according to claim 7, wherein the circuit pattern is formed in the resist upper layer film by a photolithography with a wavelength of 10 nm or more and 300 nm or less, direct lithography with electron beam, nanoimprinting, or a combination thereof.
 13. The patterning process according to claim 7, wherein alkali development or organic solvent development is employed as a development method.
 14. The patterning process according to claim 7, wherein the body to be processed is a semiconductor device substrate, a metal film, a metal carbide film, a metal oxide film, a metal nitride film, a metal oxycarbide film, or a metal oxynitride film.
 15. The patterning process according to claim 14, wherein the metal is silicon, titanium, tungsten, hafnium, zirconium, chromium, germanium, copper, silver, gold, aluminum, indium, gallium, arsenic, palladium, iron, tantalum, iridium, molybdenum, or an alloy thereof.
 16. A polymer comprising a repeating unit shown by the following general formula (1A) as a partial structure,

wherein: AR₁ and AR₂ each represent a benzene ring or a naphthalene ring which optionally have a substituent; W₁ represents any in the following general formula (1B), and the polymer optionally contains two kinds of W₁ in combination:

wherein: each R₁ is any in the following general formula (1C),

and R₂ is any in the following general formula (1D),

and W₂ represents a divalent organic group having 1 to 80 carbon atoms.
 17. A polymer comprising a repeating unit shown by the following general formula (1A) as a partial structure,

wherein: AR₁ and AR₂ each represent a benzene ring or a naphthalene ring which optionally have a substituent; W₁ represents any in the following general formula (1B), and the polymer optionally comprises two or more kinds of W₁ in combination,

wherein: each R₁ represents a monovalent organic group having 1 to 10 carbon atoms and an unsaturated bond; and R₂ represents a monovalent organic group having 6 to 20 carbon atoms and one or more aromatic rings; and W₂ is any in the following general formula (1E),

wherein: AR₃ and AR₄ each represent a benzene ring or a naphthalene ring which optionally have a substituent; and W₃ represents a divalent organic group having 6 to 50 carbon atoms and one or more aromatic rings.
 18. The polymer according to claim 17, wherein the divalent organic group represented by W₃ in the general formula (1E) is any in the following general formula, 